Magazine Articles |
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Martrenchard S. (2014). Luminescence. Encyclopædia Universalis, .
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Nodin, L., Méallet-Renault, R., & Piard, J. (2014). Séparation et étude des pigments des épinards par spectrofluorimétrie. Bulletin de l’Union des Physiciens, 961, 293–310.
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Schull, G., Boer-Duchemin, E., Comtet, G., & Dujardin, G. (2014). Émission de lumière sous la pointe d’un microscope à effet tunnel. Reflets de la Physique, 38, 4–9.
Résumé: Une source de lumière de dimension atomique est réalisée à l’aide d’un microscope à effet tunnel (STM). Cette source de photons est localisée à la jonction entre une pointe, que l’on peut déplacer avec une précision atomique, et un échantillon métallique. Elle se distingue par une excitation de nature électronique (le courant tunnel), et fait également intervenir des plasmons de surface présents dans la jonction tunnel. La jonction tunnel est ainsi une « source électrique » de plasmons de surface. Cependant, on est encore loin de comprendre le fonctionnement de cette source optique et plasmonique et d’en avoir exploité toutes les possibilités.
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Peer-reviewed Publications |
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Alarcón, L. S., Jia, J., Carrera, A., Esaulov, V. A., Ascolani, H., Gayone, J. E., Sánchez, E. A., & Grizzi, O. (2014). Direct recoil spectroscopy of adsorbed atoms and self-assembled monolayers on Cu(001). Vacuum, 105, 80–87.
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Amiaud, L., Houplin, J., Bourdier, M., Humblot, V., Azria, R., Pradier, C. - M., & Lafosse, A. (2014). Low-energy electron induced resonant loss of aromaticity: consequences on cross-linking in terphenylthiol SAMs. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16(3), 1050–1059.
Résumé: Aromatic self-assembled monolayers (SAMs) can be used as negative tone electron resists in functional surface lithographic fabrication. A dense and resistant molecular network is obtained under electron irradiation through the formation of a cross-linked network. The elementary processes and possible mechanisms involved were investigated through the response of a model aromatic SAM, p-terphenylthiol SAM, to low-energy electron (0-10 eV) irradiation. Energy loss spectra as well as vibrational excitation functions were measured using High Resolution Electron Energy Loss Spectroscopy (HREELS). A resonant electron attachment process was identified around 6 eV through associated enhanced excitation probability of the CH stretching modes [small nu](CH)ph at 378 meV. Electron irradiation at 6 eV was observed to induce a peak around 367 meV in the energy loss spectra, attributed to the formation of sp3-hybridized CHx groups within the SAM. This partial loss of aromaticity is interpreted to be the result of resonance formation, which relaxes by reorganization and/or CH bond dissociation mechanisms followed by radical chain reactions. These processes may also account for cross-linking induced by electron irradiation of aromatic SAMs in general.
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Asselin, P., Soulard, P., Madebène, B., Goubet, M., Huet, T. R., Georges, R., Pirali, O., & & Roy, P. (2014). The cyclic ground state structure of the HF trimer revealed by far infrared jet-cooled Fourier transform spectroscopy. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 4797–4806.
Résumé: The rovibrationally resolved Fourier transform (FT) far infrared (FIR) spectra of two intermolecular librations of (HF)3, namely the in-plane n6 and out-of-plane n4 bending fundamentals centered, respectively, at about 494 cm1 and 602 cm1, have been recorded for the first time under jet-cooled conditions using the supersonic jet of the Jet-AILES apparatus. The simultaneous rotational analysis of 245 infrared transitions belonging to both bands enabled us to determine the ground state (GS), n6 and n4 rotational and centrifugal distortion constants. These results provided definite experimental answers to the structure of such a weakly
bound trimer: firstly the vibrationally averaged planarity of cyclic (HF)3, also supported by the very small value of the inertia defect obtained in the GS, secondly the slight weakening of the hydrogen bond in the intermolecular excited states evidenced from the center of mass separations of the HF constituents
determined in the ground, n6 = 1 and n4 = 1 states of (HF)3 as well as the decrease of the fitted rotational constants upon excitation. Finally, lower bounds of about 2 ns on n6 and n4 state lifetimes could be derived from the deconvolution of experimental linewidths. Such long lifetimes highlight the interest in probing low frequency intermolecular motions of molecular complexes to get rid of constraints related to the vibrational dynamics of coupled anharmonic vibrations at higher energy, resulting in loss of rotational information.
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Atkinson, P., Eddrief, M., Etgens, V. H., Khemliche, H., Debiossac, M., Momeni, A., Mulier, M., Lalmi, B., & Roncin, P. (2014). Dynamic grazing incidence fast atom diffraction during molecular beam epitaxial growth of GaAs. Appl. Phys. Lett., 105(2).
Résumé: A Grazing Incidence Fast Atom Diffraction (GIFAD) system has been mounted on a commercial molecular beam epitaxy chamber and used to monitor GaAs growth in real-time. In contrast to the conventionally used Reflection High Energy Electron Diffraction, all the GIFAD diffraction orders oscillate in phase, with the change in intensity related to diffuse scattering at step edges. We show that the scattered intensity integrated over the Laue circle is a robust method to monitor the periodic change in surface roughness during layer-by-layer growth, with oscillation phase and amplitude independent of incidence angle and crystal orientation. When there is a change in surface reconstruction at the start of growth, GIFAD intensity oscillations show that there is a corresponding delay in the onset of layer-by-layer growth. In addition, changes in the relative intensity of different diffraction orders have been observed during growth showing that GIFAD has the potential to provide insight into the preferential adatom attachment sites on the surface reconstruction during growth. (C) 2014 AIP Publishing LLC.
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Bergeron, H., & Gazeau, J. P. (2014). Integral quantizations with two basic examples. Annals of Physics, 344, 43–68.
Résumé: The paper concerns integral quantization, a procedure based on operator-valued measure and resolution of the identity. We insist on covariance properties in the important case where group representation theory is involved. We also insist on the inherent probabilistic aspects of this classical quantum map. The approach includes and generalizes coherent state quantization. Two applications based on group representation are carried out. The first one concerns the Weyl-Heisenberg group and the euclidean plane viewed as the corresponding phase space. We show that a world of quantizations exist, which yield the canonical commutation rule and the usual quantum spectrum of the harmonic oscillator. The second one concerns the affine group of the real line and gives rise to an interesting regularization of the dilation origin in the half plane viewed as the corresponding phase space. (C) 2014 Elsevier Inc. All rights reserved.
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Bergeron, H., Curado, E. M. F., Gazeau, J. P., & Rodrigues, L. M. C. S. (2014). Quantizations from (P)OVM's. J. Phys.: Conf. Ser., 512, 012032.
Résumé: We explain the powerful role that operator-valued measures can play in quantizing any set equipped with a measure, for instance a group (resp. group coset) with its invariant (resp. quasi-invariant) measure. Coherent state quantization is a particular case. Such integral quantizations are illustrated with two examples based on the Weyl-Heisenberg group and on the affine group respectively. An interesting application of the affine quantization in quantum cosmology is mentioned, and we sketch a construction of new coherent states for the hydrogen atom.
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Bergeron, H., Dapor, A., Gazeau, J. P., & Malkiewicz, P. (2014). Smooth big bounce from affine quantization. Physical Review D, 89(8), 083522.
Résumé: We examine the possibility of dealing with gravitational singularities on a quantum level through the use of coherent state or wavelet quantization instead of canonical quantization. We consider the Robertson-Walker metric coupled to a perfect fluid. It is the simplest model of a gravitational collapse, and the results obtained here may serve as a useful starting point for more complex investigations in the future. We follow a quantization procedure based on affine coherent states or wavelets built from the unitary irreducible representation of the affine group of the real line with positive dilation. The main issue of our approach is the appearance of a quantum centrifugal potential allowing for regularization of the singularity, essential self-adjointness of the Hamiltonian, and unambiguous quantum dynamical evolution.
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Bergeron, H., Hrycyna, O., Malkiewicz, P., & Piechocki, W. (2014). Quantum theory of the Bianchi II model. Physical Review D, 90(4), 044041.
Résumé: We describe the quantum evolution of the vacuum Bianchi II universe in terms of the transition amplitude between two asymptotic quantum Kasner-like states. For large values of the momentum variable, the classical and quantum calculations give similar results. The difference occurs for small values of this variable due to the Heisenberg uncertainty principle. Our results can be used, to some extent, as a building block of the quantum evolution of the vacuum Bianchi IX universe.
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Bon, P., Lécart, S., Fort, E., & Lévêque-Fort, S. (2014). Fast Label-Free Cytoskeletal Network Imaging in Living Mammalian Cells. Biophysical Journal, 106(8), 1588–1595.
Résumé: We present a full-field technique that allows label-free cytoskeletal network imaging inside living cells. This noninvasive technique allows monitoring of the cytoskeleton dynamics as well as interactions between the latter and organelles on any timescale. It is based on high-resolution quantitative phase imaging (modified Quadriwave lateral shearing interferometry) and can be directly implemented using any optical microscope without modification. We demonstrate the capability of our setup on fixed and living Chinese hamster ovary cells, showing the cytoskeleton dynamics in lamellipodia during protrusion and mitochondria displacement along the cytoskeletal network. In addition, using the quantitative function of the technique, along with simulation tools, we determined the refractive index of a single tubulin microtubule to be ntubu=2.36±0.6 at ?=527 nm.
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Boucher G., Eckstein A., Orieux A., Favero I., Leo G., Coudreau T., Keller A., Milman P., & Ducci S. (2014). Polarization-entanglement generation and control in a counterpropagating phase-matching geometry. Phys. Rev. A, 89, 033815.
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Bouchet, A., Altnoder, J., Broquier, M., & Zehnacker, A. (2014). IR-UV spectroscopy of jet-cooled 1-indanol: Restriction of the conformational space by hydration. JOURNAL OF MOLECULAR STRUCTURE, 1076, 344–351.
Résumé: The effect of hydration on a flexible amphiphilic molecule has been studied on the example of 1-hydroxyindan (1-indanol). Studies in jet-cooled conditions by means of resonance-enhanced two-photon ionization and IR-UV double resonance experiments show that the mono-hydrate 1-indanol(H2O) is formed in a dominant isomer, as well as the di-hydrate 1-indanol(H2O)(2). 1-Indanol(H2O) favors a cooperative hydrogen bond pattern with -OH center dot center dot center dot O(H)-H center dot center dot center dot pi it topology, while 1-indanol(H2O)(2) forms a cyclic hydrogen bond network with three OH center dot center dot center dot O interactions. The single conformation observed for the hydrates contrasts with the bare molecule which shows two dominant conformations, with the hydroxyl in axial or in equatorial position, respectively. Hydration therefore results in a restriction of the conformational space and conformational locking. (C) 2014 Elsevier B.V. All rights reserved.
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Boulet, C., Ma, Q., & and Thibault, F. (2014). Line interference using a refined Robert-Bonamy formalism: the test case of the isotropic Raman spectra of autoperturbed N2. JOURNAL OF CHEMICAL PHYSICS, 140(8), 084310.
Résumé: A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys.139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N2 for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While in the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N2, opening the way to the analysis of more complex molecular systems.
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Boye-Peronne, S., Gauyacq, D., & Lievin, J. (2014). Theoretical description of electronically excited vinylidene up to 10 eV: First high level ab initio study of singlet valence and Rydberg states. JOURNAL OF CHEMICAL PHYSICS, 141(17), 174317.
Résumé: The first quantitative description of the Rydberg and valence singlet electronic states of vinylidene lying in the 0-10 eV region is performed by using large scale ab initio calculations. A deep analysis of Rydberg-valence interactions has been achieved thanks to the comprehensive information contained in the accurate Multi-Reference Configuration Interaction wavefunctions and an original population analysis highlighting the respective role played by orbital and state mixing in such interactions. The present theoretical approach is thus adequate for dealing with larger than diatomic Rydberg systems. The nine lowest singlet valence states have been optimized. Among them, some are involved in strong Rydberg-valence interactions in the region of the Rydberg state equilibrium geometry. The Rydberg states of vinylidene present a great similarity with the acetylene isomer, concerning their quantum defects and Rydberg molecular orbital character. As in acetylene, strong s-d mixing is revealed in the n = 3 s-d supercomplex. Nevertheless, unlike in acetylene, the close-energy of the two vinylidene ionic cores (2)A1 and (2)B1 results into two overlapped Rydberg series. These Rydberg series exhibit local perturbations when an accidental degeneracy occurs between them and results in avoided crossings. In addition, some Deltal = 1 (s-p and p-d) mixings arise for some Rydberg states and are rationalized in term of electrostatic interaction from the electric dipole moment of the ionic core. The strongest dipole moment of the (2)B1 cationic state also stabilizes the lowest members of the n = 3 Rydberg series converging to this excited state, as compared to the adjacent series converging toward the (2)A1 ionic ground state. The overall energies of vinylidene Rydberg states lie above their acetylene counterpart. Finally, predictions for optical transitions in singlet vinylidene are suggested for further experimental spectroscopic characterization of vinylidene.
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Brechignac, P., Garcia, G. A., Falvo, C., Joblin, C., Kokkin, D., Bonnamy, A., Parneix, P., Pino, T., Pirali, O., Mulas, G., & Nahon, L. (2014). Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation. JOURNAL OF CHEMICAL PHYSICS, 141(16), 164325.
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Breinlich, C., Buchholz, M., Moors, M., Le Moal, S., Becker, C., & Wandelt, K. (2014). Scanning tunnelling microscopy investigation of ultrathin titanium oxide films grown on Pt3Ti(111). JOURNAL OF PHYSICAL CHEMISTRY C, 118, 6186–6192.
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Calvo, F., Falvo, C., & Parneix, P. (2014). Atomistic Modeling of Vibrational Action Spectra in Polyatomic Molecules: Nuclear Quantum Effects. JOURNAL OF PHYSICAL CHEMISTRY A, 118(29), 5427–5436.
Résumé: The response of a polyatonaic molecule to an infrared (IR) laser pulse of varying frequency has been simulated by classical molecular dynamics simulations and by quantum methods based on the path-integral framework (PIMD), as well as quantum thermal baths (QTBs). The outcome of the trajectories was subsequently processed to predict a dissociation spectrum, from the precalculated rate constant. Naphthalene described by a tight-binding potential energy surface was chosen as a testing ground for the present problem, possibly emitting an hydrogen atom after a 12 ps long pulse. At low field intensities, the heating efficiency of the pulse is found to vary similarly as the IR absorption spectrum for all methods considered, reflecting the validity of linear response in this regime. At fields that are sufficiently high to induce statistical dissociation over mass spectrometry timescales, marked differences appear with the spectral features exhibiting additional broadenings and redshift, especially for quantum mechanical descriptions of nuclear motion. Those excessive broadenings are mostly caused by anharmonicities but also convey the inherent approximations of the semidassical QTB method and point at limitations of the PIMD simulations when used in such strong out-of-equilibrium conditions.
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Cao, S., Le Moal, E., Boer-Duchemin, E., Dujardin, G., Drezet, A., & Huant, S. (2014). Cylindrical vector beams of light from an electrically excited plasmonic lens. Appl. Phys. Lett., 105(11), 111103.
Résumé: The production of cylindrical vector beams from a low-energy, electric, microscale light source is demonstrated both experimentally and theoretically. This is achieved by combining a “plasmonic lens” with the ability to locally and electrically excite propagating surface plasmons on gold films. The plasmonic lens consists of concentric circular subwavelength slits that are etched in a thick gold film. The local excitation arises from the inelastic tunneling of electrons from the tip of a scanning tunneling microscope. We report on the emission of radially polarized beams with an angular divergence of less than 4°.
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Capello, M. C., Broquier, M., Ishiuchi, S. I., Sohn, W. Y., Fujii, M., Dedonder-Lardeux, C., Jouvet, C., & Pino, G. A. (2014). Fast Nonradiative Decay in o-Aminophenol. Journal of Physical Chemistry A, 118, 2056–2062.
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Celia, E., Amigoni, S., de Givenchy, E. T., Pieters, G., Gaucher, A., Prim, D., Audibert, J. F., Meallet-Renault, R., Pansu, R., & Guittard, F. (2014). A spiral designed surface based on amino-perylene grafted polyacrylic acid. Chemical Communications, 50(81), 12034–12036.
Résumé: This communication shows the possibility of inducing spontaneous special surface organisation by means of grafting a fluorescent aminobenzo[g,h,i]perylene derivative onto surface grown polyacrylic chains.
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Chaudret, R., de Courcy, B., Contreras-Garcia, J., Gloaguen, E., Zehnacker-Rentien, A., Mons, M., & Piquemal, J. P. (2014). Unraveling non-covalent interactions within flexible biomolecules: from electron density topology to gas phase spectroscopy. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16(21), 9876–9891.
Résumé: The NCI (Non-Covalent Interactions) method, a recently-developed theoretical strategy to visualize weak non-covalent interactions from the topological analysis of the electron density and of its reduced gradient, is applied in the present paper to document intra- and inter-molecular interactions in flexible molecules and systems of biological interest in combination with IR spectroscopy. We first describe the conditions of application of the NCI method to the specific case of intramolecular interactions. Then we apply it to a series of stable conformations of isolated molecules as an interpretative technique to decipher the different physical interactions at play in these systems. Examples are chosen among neutral molecular systems exhibiting a large diversity of interactions, for which an extensive spectroscopic characterization under gas-phase isolation conditions has been obtained using state-of-the-art conformer-specific experimental techniques. The interactions presently documented range from weak intra-molecular H-bonds in simple amino-alcohols, to more complex patterns, with interactions of various strengths in model peptides, as well as in chiral bimolecular systems, where invaluable hints for the understanding of chiral recognition are revealed. We also provide a detailed technical appendix, which discusses the choices of cut-offs as well as the applicability of the NCI analysis to specific constrained systems, where local effects require attention. Finally, the NCI technique provides IR spectroscopists with an elegant visualization of the interactions that potentially impact their vibrational probes, namely the OH and NH stretching motions. This contribution illustrates the power and the conditions of use of the NCI technique, with the aim of providing an easy tool for all chemists, experimentalists and theoreticians, for the visualization and characterization of the interactions shaping complex molecular systems.
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Chin, W., Chevalier, M., Thon, R., Pollet, R., Ceponkus, J., & Crepin, C. (2014). Photochemistry of glycolaldehyde in cryogenic matrices. JOURNAL OF CHEMICAL PHYSICS, 140(22), 224319.
Résumé: The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S-0, S-1, and T-1 states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase. (C) 2014 AIP Publishing LLC.
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Coudert, L. H., Martin-Drumel, M. - A., & Pirali, O. (2014). Analysis of the high-resolution water spectrum up to the Second Triad and to J=30. JOURNAL OF MOLECULAR SPECTROSCOPY, 303, 36–41.
Résumé: We report high temperature spectroscopic measurements of water vapor carried out in the far infrared domain. The new data set contains numerous transitions characterized by a J-value larger than 30 and allows us to reach rotational levels of water for which information was either unavailable or inaccurate. This new data set, along with previously published microwave, far infrared, and infrared measurements, is fitted using a modified version of the Bending Rotation approach and allows us to perform the first analysis of the high-resolution spectrum of water vapor up to J = 30 for the ground and (010) states, up to J = 27 for the First Triad States, and up to J = 19 for the Second Triad States. The results of the analysis are used to build a spectroscopic database supporting high-resolution investigations performed at temperatures as high as 1500 K.
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Couturier-Tamburelli, I., Pietri, N., Crepin, C., Turowski, M., Guillemin, J. - C., & Kolos, R. (2014). Synthesis and spectroscopy of cyanotriacetylene (HC7N) in solid argon. Journal Of Chemical Physics, 140(4), 044329.
Résumé: UV laser irradiations of cryogenic solid argon matrices doped with a mixture of acetylene and cyanodiacetylene (HC5N) resulted in the formation of a longer carbon-nitrogen chain, cyanotriacetylene (HC7N). The identification of this species was accomplished based on IR vibrational spectroscopy (including the study of isotopically labeled compounds), on electronic luminescence spectroscopy, and on theoretical predictions. Additionally, IR absorption bands recognized as due to HC7N were detected in photolysed Ar matrices doped with a cyanoacetylene/diacetylene mixture; this assignment was confirmed with the mass spectrometry of gases released upon the warm-up of the sample. (C) 2014 AIP Publishing LLC.
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Cuisset, A., Gruet, S., Pirali, O., Chamaille, T., & Mouret, G. (2014). Synchrotron FT-FIR spectroscopy of nitro-derivatives vapors: New spectroscopic signatures of explosive taggants and degradation products. SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 132, 838–845.
Résumé: We report on the first successful rovibrational study of gas phase mononitrotoluene and dinitrotoluene in the TeraHertz/Far-Infrared (THz/FIR) spectral domain. Using the AILES beamline of the synchrotron SOLEIL and a Fourier Transform spectrometer connected to multipass cells, the low-energy vibrational cross-sections of the different isomers of mononitrotoluene have been measured and compared to calculated spectra with the density functional theory including the anharmonic contribution. The active FIR modes of 2,4 and 2,6 dinitrotoluene have been assigned to the vibrational bands measured by Fourier Transform FIR spectroscopy of the gas-phase molecular cloud produced in an evaporating/recondensating system. This study highlights the selectivity of gas phase THz/FIR spectroscopy allowing an unambiguous recognition and discrimination of nitro-aromatic compounds used as explosive taggants.
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Dartois, E., Engrand, C., Brunetto, R., Duprat, J., Pino, T., Quirico, E., Remusat, L., Bardin, N., Briani, G., Mostefaoui, S., Morinaud, G., Crane, B., Szwec, N., Delauche, L., Jamme, F., Sand, C., & Dumas, P. (2014). Interstellar and interplanetary carbonaceous solids in the laboratory. Geochemical Journal, 48(6), 511–518.
Résumé: The interstellar medium (ISM) is a physico-chemical laboratory where extreme conditions are encountered and where particular environmental parameters (e.g., density, reactant nature, radiation, temperature, time scales) define the composition of matter. With present observational possibilities, the fundamental question regarding the possible link between ISM and solar system samples can be addressed by astrophysicists, planetologists, and cosmochemists. This article focuses on observations of diffuse ISM and dust components of molecular clouds, setting constraints on the composition of organic solids and large molecules associated with matter cycling in the Galaxy. This study aims at drawing some commonalities and differences between the materials found in the Solar System and those found in interstellar dust.
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Debiossac M. and Roncin P. (2014). Atomic diffraction under oblique incidence: An analytical expression. Phys. Rev. A., 90, 054701.
Résumé: The semiclassical perturbation method developed by Henkel et al. [J. Phys. II 4, 1955 (1994)] to model
cold-atom diffraction by optical standing waves, is applied to the diffraction of fast atoms on crystal surfaces at
grazing incidence (GIFAD or FAD).We first show that the interaction time and interaction length embedded in the
obliquity factor is well suited to explain the transition from three-dimensional to two-dimensional (2D) diffraction.
The situation of a slightly misaligned primary beam, corresponding to oblique incidence in the effective 2Dsystem,
is addressed pointing out discrepancies such as the absence of net deflection of the atomic beam. Guided by
time-reversal considerations, we propose an arbitrarily symmetrized form significantly improving the agreement
with experimental data recorded in oblique incidence.
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Debiossac, M., Zugarramurdi, A., Lunca-Popa, P., Momeni, A., Khemliche, H., Borisov, A. G., & Roncin, P. (2014). Transient Quantum Trapping of Fast Atoms at Surfaces. Phys. Rev. Lett., 112(2).
Résumé: We report on the experimental observation and theoretical study of the bound state resonances in fast atom diffraction at surfaces. In our studies, the He-4 atom beam has been scattered from a high-quality LiF(001) surface at very small grazing incidence angles. In this regime, the reciprocal lattice vector exchange with the surface allows transient trapping of the 0.3-0.5 keV projectiles into the quasistationary states bound by the attractive atom-surface potential well which is only 10 meV deep. Analysis of the linewidths of the calculated and measured resonances reveals that prior to their release, the trapped projectiles preserve their coherence over travel distances along the surface as large as 0.2 μm, while being in average only at some angstroms in front of the last atomic plane.
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Debiossac, M. and Z., A. and Khemliche, H. and Roncin, P. and Borisov, A. G. and Momeni, A. and Atkinson, P. and Eddrief, M. and Finocchi, F. and Etgens, V. H. (2014). Combined experimental and theoretical study of fast atom diffraction on the β2(2×4) reconstructed GaAs(001) surface. Phys. Rev. B, 90(15), 155308.
Résumé: A grazing incidence fast atom diffraction (GIFAD or FAD) setup, installed on a molecular beam epitaxy chamber, has been used to characterize the β2(2×4) reconstruction of a GaAs(001) surface at 530∘C under an As4 overpressure. Using a 400-eV 4He beam, high-resolution diffraction patterns with up to eighty well-resolved diffraction orders are observed simultaneously, providing a detailed fingerprint of the surface structure. Experimental diffraction data are in good agreement with results from quantum scattering calculations based on an ab initio projectile-surface interaction potential. Along with exact calculations, we show that a straightforward semiclassical analysis allows the features of the diffraction chart to be linked to the main characteristics of the surface reconstruction topography. Our results demonstrate that GIFAD is a technique suitable for measuring in situ the subtle details of complex surface reconstructions. We have performed measurements at very small incidence angles, where the kinetic energy of the projectile motion perpendicular to the surface can be reduced to less than 1 meV. This allowed the depth of the attractive van der Waals potential well to be estimated as −8.7 meV in very good agreement with results reported in literature.
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Deshayes, S., & Gref, R. (2014). Synthetic and bioinspired cage nanoparticles for drug delivery. Nanomedicine, 9(10), 1545–1564.
Résumé: Nanotechnology has the potential to revolutionize drug delivery, but still faces some limitations. One of the main issues regarding conventional nanoparticles is their poor drug-loading and their early burst release. Thus, to overcome these problems, researchers have taken advantage of the host-guest interactions that drive some assemblies to form cage molecules able to strongly entrap their cargo and design new nanocarriers called cage nanoparticles. These systems can be classified into two categories: bioinspired nanosystems such as virus-like particles, ferritin, small heat shock protein: and synthetic host-guest supramolecular systems that require engineering to actually form supramolecular nanoassemblies. This review will highlight the recent advances in cage nanoparticles for drug delivery with a particular focus on their biomedical applications.
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Dopfer, O., Patzer, A., Chakraborty, S., Alata, I., Omidyan, R., Broquier, M., Dedonder, C., & Jouvet, C. (2014). Electronic and vibrational spectra of protonated benzaldehyde-water clusters, BZ-(H2O)(n <= 5) H+: Evidence for ground-state proton transfer to solvent for n >= 3. Journal of Chemical Physics, 140(12), 124314.
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Fan, C., Poumellec, B., Desmarchelier, R., Zeng, H., Bourguignon, B., Chen, G., & Lancry, M. (2014). Asymmetric orientational writing dependence on polarization and direction in Li2O–Nb2O5–SiO2 glass with femtosecond laser irradiation. Appl. Phys. B, 117(2), 737–747.
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Fedortchenko S., Keller A., Coudreau T., & Milman P. (2014). Finite-temperature reservoir engineering and entanglement dynamics. Phys. Rev. A, 90, 042103.
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Feraud, G., Broquier, M., Dedonder-Lardeux, C., Gregoire, G., Soorkia, S., & Jouvet, C. (2014). Photofragmentation spectroscopy of cold protonated aromatic amines in the gas phase. Phys Chem Chem Phys, 16(11), 5250–5259.
Résumé: The electronic spectra of cold protonated aromatic amines: anilineH(+) C6H5-NH3(+), benzylamineH(+) C6H5-CH2-NH3(+) and phenylethylamineH(+) C6H5-(CH2)2-NH3(+) have been investigated experimentally in a large spectral domain and are compared to those of their hydroxyl homologues. In the low energy region, the electronic spectra are similar to their neutral analogues, which reveals the pipi* character of their first excited state. A second transition is observed from 0.4 to 1 eV above the origin band, which is assigned to the excitation of the pisigma* state. In these protonated amine molecules, there is a competition between different fragmentation channels, some being specific to UV excitation i.e., not observed in low-energy collision induced dissociation experiments. Besides, for one amine a drastic change in the fragmentation branching ratio is observed within a very short energy range that reveals the complex excited state dynamics and fragmentation processes. The experimental observations can be rationalized using a simple qualitative model, the pipi*-pisigma* model [A. L. Sobolewski, W. Domcke, C. Dedonder-Lardeux and C. Jouvet, Phys. Chem. Chem. Phys., 2002, 4, 1093-1100], which predicts that the excited state dynamics is controlled by the crossing between the pipi* excited state and a pisigma* state repulsive along the XH (X being O or N) coordinate.
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Feraud, G., Dedonder-Lardeux, C., Soorkia, S., & Jouvet, C. (2014). Photo-fragmentation spectroscopy of benzylium and 1-phenylethyl cations. J Chem Phys, 140(2), 024302.
Résumé: The electronic spectra of cold benzylium (C6H5-CH2 (+)) and 1-phenylethyl (C6H5-CH-CH3 (+)) cations have been recorded via photofragment spectroscopy. Benzylium and 1-phenylethyl cations produced from electrosprayed benzylamine and phenylethylamine solutions, respectively, were stored in a cryogenically cooled quadrupole ion trap and photodissociated by an OPO laser, scanned in parts of the UV and visible regions (600-225 nm). The electronic states and active vibrational modes of the benzylium and 1-phenylethyl cations as well as those of their tropylium or methyl tropylium isomers have been calculated with ab initio methods for comparison with the spectra observed. Sharp vibrational progressions are observed in the visible region while the absorption features are much broader in the UV. The visible spectrum of the benzylium cation is similar to that obtained in an argon tagging experiment [V. Dryza, N. Chalyavi, J. A. Sanelli, and E. J. Bieske, J. Chem. Phys. 137, 204304 (2012)], with an additional splitting assigned to Fermi resonances. The visible spectrum of the 1-phenylethyl cation also shows vibrational progressions. For both cations, the second electronic transition is observed in the UV, around 33,000 cm(-1) (4.1 eV) and shows a broadened vibrational progression. In both cases the S2 optimized geometry is non-planar. The third electronic transition observed around 40,000 cm(-1) (5.0 eV) is even broader with no apparent vibrational structures, which is indicative of either a fast non-radiative process or a very large change in geometry between the excited and the ground states. The oscillator strengths calculated for tropylium and methyl tropylium are weak. Therefore, these isomeric structures are most likely not responsible for these absorption features. Finally, the fragmentation pattern changes in the second and third electronic states: C2H2 loss becomes predominant at higher excitation energies, for both cations.
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Feraud, G., Pino, T., Falvo, C., Parneix, P., Combriat, T., & Brechignac, P. (2014). Intramolecular Processes Revealed Using UV-Laser-Induced IR-Fluorescence: A New Perspective on the “Channel Three” of Benzene. JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5(7), 1083–1090.
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Gauyacq, J. - P., & Lorente, N. (2014). Excitation of bond-alternating spin-1/2 Heisenberg chains by tunnelling electrons. J. Phys. Condens. Matter., 26(39), 394005.
Résumé: Inelastic electron tunneling spectra (IETS) are evaluated for spin-1/2 Heisenberg chains showing different phases of their spin ordering. The spin ordering is controlled by the value of the two different Heisenberg couplings on the two sides of each of the chain's atoms (bond-alternating chains). The perfect anti-ferromagnetic phase, i.e. a unique exchange coupling, marks a topological quantum phase transition (TQPT) of the bond-alternating chain. Our calculations show that the TQPT is recognizable in the excited states of the chain and hence that IETS is in principle capable of discriminating the phases. We show that perfectly symmetric chains, such as closed rings mimicking infinite chains, yield the same spectra on both sides of the TQPT and IETS cannot reveal the nature of the spin phase. However, for finite size open chains, both sides of the TQPT are associated with different IETS spectra, especially on the edge atoms, thus outlining the transition.
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Gauyacq, J. P., & Lorente, N. (2014). Classical limit of a quantal nano-magnet in an anisotropic environment. Surface Science, 630, 325–330.
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Gharaibeh, M. F., El Hassan, N., Al Shorman, M. M., Bizau, J. M., Cubaynes, D., Guilbaud, S., Sakho, I., Blancard, C., & McLaughlin, B. M. (2014). K-shell photoionization of B-like atomic nitrogen ions: experiment and theory. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 47(6), 065201.
Résumé: Measurements of absolute cross sections for the K-shell photoionization of B-like atomic nitrogen ions were carried out utilizing the ion-photon merged-beam technique at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E/Delta E approximate to 13,500 was the maximum resolution achieved. We have investigated two photon energy regions: 404-409 eV and 439-442 eV. Resonance peaks found in the experimental measured cross sections are compared with theoretical estimates from the multi-configuration Dirac-Fock, R-matrix and empirical methods, allowing identification of the strong 1s -> 2p and the weaker 1s -> 3p resonances in the observed K-shell spectra of this B-like nitrogen ion.
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Gloaguen, E., Brenner, V., Alauddin, M., Tardivel, B., Mons, M., Zehnacker-Rentien, A., Declerck, V., & Aitken, D. J. (2014). Direct Spectroscopic Evidence of Hyperconjugation Unveils the Conformational Landscape of Hydrazides. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53(50), 13756–13759.
Résumé: The stereochemistry of hydrazides makes them especially interesting as building blocks for molecular design. An exhaustive conformational analysis of three model hydrazides was conducted in a conformer-selective approach by using a combination of high-level quantum chemistry calculations and vibrational spectroscopy in the gas phase and in solution. The NH stretch frequency was found to be highly sensitive to hyperconjugation, thus making it an efficient probe of the conformation of the neighboring nitrogen atom. This property greatly assisted the identification of the isomers observed experimentally in the conformer pool. A rationalization of the hydrazide conformational landscape is proposed, therefore paving the way for a better characterization of secondary structures in larger systems.
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Goubet, M., & Pirali, O. (2014). The far-infrared spectrum of azulene and isoquinoline and supporting anharmonic density functional theory calculations to high resolution spectroscopy of polycyclic aromatic hydrocarbons and derivatives. JOURNAL OF CHEMICAL PHYSICS, 140, 044322.
Résumé: In the laboratory, the acquisition and analysis of the rotationally resolved spectra of large molecular systems remain challenging. We report in this paper the rotational analysis of the ν30-GS band of azulene and the ν41-GS band of isoquinoline recorded with synchrotron-based Fourier transform absorption spectroscopy in the far-IR. As a support to rotational analyses, we employed a method based on standard density functional theory calculations performed at the anharmonic level which accurately reproduced the rotational constants of 28 vibrational states of 16 Polycyclic Aromatic Hydrocarbons (PAHs) and aza-derivatives. This method appears as an invaluable support for the spectral assignment of the very congested rotational structures of the infrared bands of PAH species and should be very helpful in the active search of these molecules in space through their pure rotational or rovibrational spectra.
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Grazon, C., Rieger, J., Charleux, B., Clavier, G., & Meallet-Renault, R. (2014). Ultrabright BODIPY-Tagged Polystyrene Nanoparticles: Study of Concentration Effect on Photophysical Properties. Journal Of Physical Chemistry C, 118(25), 13945–13952.
Résumé: Fluorescent nanomaterials are invaluable tools for bioimaging. Polymeric nanoparticles labeled with organic dyes are very promising for this purpose. It is thus very important to fully understand their photophysical properties. New fluorescent core-shell nanoparticles have been prepared. The outer part is a poly(ethylene glycol)-block-poly(acrylic acid) copolymer, and the core is a copolymer of styrene and methacrylic BODIPY fluorophore. The hydrophilic and hydrophobic parts are covalently linked, ensuring both stability and biocompatibility. We prepared nanoparticles with increasing amounts of BODIPY, from 500 to 5000 fluorophores per particles. Increasing the concentration of BODIPY lowers both the fluorescence quantum yield and the lifetime. However, the brightness of the individual particles increases up to 8 X 10(7). To understand the loss of fluorescence efficiency, fluorescence decays have been recorded and fitted with a mathematical model using a stretched exponential function. This result gives an insight into the fluorophore arrangement within the hydrophobic core.
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Gruet, S., Goubet, M., & Pirali, O. (2014). High resolution measurements supported by electronic structure calculations of two naphthalene derivatives: [1,5]- and [1,6]-naphthyridine-Estimation of the zero point inertial defect for planar polycyclic aromatic compounds. JOURNAL OF CHEMICAL PHYSICS, 140(23), 234308.
Résumé: Polycyclic aromatic hydrocarbons (PAHs) molecules are suspected to be present in the interstellar medium and to participate to the broad and unresolved emissions features, the so-called unidentified infrared bands. In the laboratory, very few studies report the rotationally resolved structure of such important class of molecules. In the present work, both experimental and theoretical approaches provide the first accurate determination of the rotational energy levels of two diazanaphthalene: [1,5]- and [1,6]-naphthyridine. [1,6]-naphthyridine has been studied at high resolution, in the microwave (MW) region using a Fourier transform microwave spectrometer and in the far-infrared (FIR) region using synchrotron-based Fourier transform spectroscopy. The very accurate set of ground state (GS) constants deduced from the analysis of the MW spectrum allowed the analysis of the most intense modes in the FIR (nu(38)-GS centered at about 483 cm(-1) and nu(34)-GS centered at about 842 cm(-1)). In contrast with [1,6]-naphthyridine, pure rotation spectroscopy of [1,5]-naphthyridine cannot be performed for symmetry reasons so the combined study of the two intense FIR modes (nu(22)-GS centered at about 166 cm(-1) and nu(18)-GS centered at about 818 cm(-1)) provided the GS and the excited states constants. Although the analysis of the very dense rotational patterns for such large molecules remains very challenging, relatively accurate anharmonic density functional theory calculations appeared as a highly relevant supporting tool to the analysis for both molecules. In addition, the good agreement between the experimental and calculated infrared spectrum shows that the present theoretical approach should provide useful data for the astrophysical models. Moreover, inertial defects calculated in the GS (Delta(GS)) of both molecules exhibit slightly negative values as previously observed for planar species of this molecular family. We adjusted the semi-empirical relations to estimate the zero-point inertial defect (Delta(0)) of polycyclic aromatic molecules and confirmed the contribution of low frequency out-of-plane vibrational modes to the GS inertial defects of PAHs, which is indeed a key parameter to validate the analysis of such large molecules.
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Hamoudi, H., Uosaki, K., Ariga, K., & Esaulov, V. A. (2014). Going beyond the self-assembled monolayer: metal intercalated dithiol multilayers and their conductance. RSC Adv., 4(75), 39657.
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Hartmann, J. M., Boulet, C., Vander Auwera J., El Hamzaoui, H., Capoen, B., & and Bouazaoui, M. (2014). Line broadening of confined CO gas. From molecule-wall to molecule-molecule collisions with pressure. JOURNAL OF CHEMICAL PHYSICS, 140(6), 064302.
Résumé: The infrared absorption in the fundamental band of CO gas confined in porous silica xerogel has been recorded at room temperature for pressures between about 5 and 920 hPa using a high resolution Fourier transform spectrometer. The widths of individual lines are determined from fits of measured spectra and compared with ab initio predictions obtained from requantized classical molecular dynamics simulations. Good agreement is obtained from the low pressure regime where the line shapes are governed by molecule-wall collisions to high pressures where the influence of molecule-molecule interactions dominates. These results, together with those obtained with a simple analytical model, indicate that both mechanisms contribute in a practically additive way to the observed linewidths. They also confirm that a single collision of a molecule with a wall changes its rotational state. These results are of interest for the determination of some characteristics of the opened porosity of porous materials through optical soundings.
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Helml, W., Maier, A. R., Schweinberger, W., Grguras, I., Radcliffe, P., Doumy, G., Roedig, C., Gagnon, J., Messerschmidt, M., Schorb, S., Bostedt, C., Gruener, F., DiMauro, L. F., Cubaynes, D., Bozek, J. D., Tschentscher, T., Costello, J. T., Meyer, M., Coffee, R., Duesterer, S., Cavalieri, A. L., & Kienberger, R. (2014). Measuring the temporal structure of few-femtosecond free-electron laser X-ray pulses directly in the time domain. NATURE PHOTONICS, 8(12), 950–957.
Résumé: Short-wavelength free-electron lasers are now well established as essential and unrivalled sources of ultrabright coherent X-ray radiation. One of the key characteristics of these intense X-ray pulses is their expected few-femtosecond duration. No measurement has succeeded so far in directly determining the temporal structure or even the duration of these ultrashort pulses in the few-femtosecond range. Here, by deploying the so-called streaking spectroscopy technique at the Linac Coherent Light Source, we demonstrate a non-invasive scheme for temporal characterization of X-ray pulses with sub-femtosecond resolution. This method is independent of photon energy, decoupled from machine parameters, and provides an upper bound on the X-ray pulse duration. We measured the duration of the shortest X-ray pulses currently available to be on average no longer than 4.4 fs. Analysing the pulse substructure indicates a small percentage of the free-electron laser pulses consisting of individual high-intensity spikes to be on the order of hundreds of attoseconds.
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Henchy, C., McCaffrey, J. G., Arabei, S., Pavich, T., Galaup, J. - P., Shafizadeh, N., & Crepin, C. (2014). Free base tetraazaporphine isolated in inert gas hosts: Matrix influence on its spectroscopic and photochemical properties. JOURNAL OF CHEMICAL PHYSICS, 141(12), 124303.
Résumé: The absorption, fluorescence, and excitation spectra of free base tetraazaporphine (H(2)TAP) trapped in Ne, N-2, and Ar matrices have been recorded at cryogenic temperatures. Normal Raman spectra of H(2)TAP were recorded in KBr discs and predicted with density functional theory (DFT) using large basis sets calculations. The vibrational frequencies observed in the Raman Spectrum exhibit reasonable agreement with those deduced from the emission spectra, as well as with frequencies predicted from large basis set DFT computations. The upper state vibrational frequencies, obtained from highly resolved, site selected excitation spectra, are consistently lower than the ground state frequencies. This contrasts with the situation in free base phthalocyanine, where the upper state shows little changes in vibrational frequencies and geometry when compared with the ground state. Investigations of the photochemical properties of H(2)TAP isolated in the three matrices have been performed using the method of persistent spectral hole-burning (PSHB). This technique has been used to reveal sites corresponding to distinct N-H tautomers which were not evident in the absorption spectra. An analysis of the holes and antiholes produced with PSHB in the Q(x) (0-0) absorption band made it possible to identify inter-conversion of distinct host sites.
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Ideguchi, T., Poisson, A., Guelachvili, G., Picque, N., & Hansch, T. W. (2014). Adaptive real-time dual-comb spectroscopy. Nature Communications, 5, 3375.
Résumé: The spectrum of a laser frequency comb consists of several hundred thousand equally spaced lines over a broad spectral bandwidth. Such frequency combs have revolutionized optical frequency metrology and they now hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite an intriguing potential for the measurement of molecular spectra spanning tens of nanometres within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the demanding stability requirements of the laser combs. Here we overcome this difficulty and experimentally demonstrate a concept of real-time dual-comb spectroscopy, which compensates for laser instabilities by electronic signal processing. It only uses free-running mode-locked lasers without any phase-lock electronics. We record spectra spanning the full bandwidth of near-infrared fibre lasers with Doppler-limited line profiles highly suitable for measurements of concentrations or line intensities. Our new technique of adaptive dual-comb spectroscopy offers a powerful transdisciplinary instrument for analytical sciences.
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Ivanov, S. V., Boulet, C., Buzykin, O. G., & and Thibault, F. (2014). Line mixing effects in isotropic Raman spectra of pure N2 : a classical trajectory study. JOURNAL OF CHEMICAL PHYSICS, 141(18), 184306.
Résumé: Line mixing effects in the Q branch of pure N2 isotropic Raman scattering are studied at room temperature using a classical trajectory method. It is the first study using an extended modified version of Gordon's classical theory of impact broadening and shift of rovibrational lines. The whole relaxation matrix is calculated using an exact 3D classical trajectory method for binary collisions of rigid N2 molecules employing the most up-to-date intermolecular potential energy surface (PES). A simple symmetrizing procedure is employed to improve off-diagonal cross-sections to make them obeying exactly the principle of detailed balance. The adequacy of the results is confirmed by the sum rule. The comparison is made with available experimental data as well as with benchmark fully quantum close coupling [F. Thibault, C. Boulet, and Q. Ma, J. Chem. Phys. 140, 044303 (2014)] and refined semi-classical Robert-Bonamy [C. Boulet, Q. Ma, and F. Thibault, J. Chem. Phys. 140, 084310 (2014)] results. All calculations (classical, quantum, and semi-classical) were made using the same PES. The agreement between classical and quantum relaxation matrices is excellent, opening the way to the analysis of more complex molecular systems.
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Jacovella, U., Holland, D. M. P., Boyé-Péronne, S., Joyeux, D., Archer, L. E., de Oliveira, N., Nahon, L., Lucchese, R. R., Xu, H., & Pratt, S. T. (2014). High-resolution photoabsorption spectrum of jet-cooled propyne. JOURNAL OF CHEMICAL PHYSICS, 141(11), 114303.
Résumé: The absolute photoabsorption cross section of propyne was recorded between 62 000 and 88 000 cm(-1) by using the vacuum-ultraviolet, Fourier-transform spectrometer at the Synchrotron Soleil. This cross section spans the region including the lowest Rydberg bands and extends above the Franck-Condon envelope for ionization to the ground electronic state of the propyne cation, (X) over tilde (+). Room-temperature spectra were recorded in a flowing cell at 0.9 cm(-1) resolution, and jet-cooled spectra were recorded at 1.8 cm(-1) resolution and a rotational temperature of similar to 100 K. The reduced widths of the rotational band envelopes in the latter spectra reveal new structure and simplify a number of assignments. Although nf Rydberg series have not been assigned previously in the photoabsorption spectrum of propyne, arguments are presented for their potential importance, and the assignment of one nf series is proposed. As expected from previous photoelectron spectra, Rydberg series are also observed above the adiabatic ionization threshold that converge to the v(3)(+) = 1 and 2 levels of the C C stretching vibration.
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Jia, J., Bendounan, A., Chaouchi, K., & Esaulov, V. A. (2014). Sulfur Interaction with Cu(100) and Cu(111) Surfaces: A Photoemission Study. J. Phys. Chem. C, , 24583–24590.
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Jia, J., Bendounan, A., Chaouchi, K., Kubsky, S., Sirotti, F., Pasquali, L., & Esaulov, V. A. (2014). Chalcogen Atom Interaction with Palladium and the Complex Molecule–Metal Interface in Thiol Self Assembly. J. Phys. Chem. C, 118(43), 24983–24994.
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Jia, J., Giglia, A., Flores, M., Grizzi, O., Pasquali, L., & Esaulov, V. A. (2014). 1,4-Benzenedimethanethiol Interaction with Au(110), Ag(111), Cu(100), and Cu(111) Surfaces: Self-Assembly and Dissociation Processes. J. Phys. Chem. C, 118(46), 26866–26876.
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Kennedy, E. T., Mosnier, J. - P., Van Kampen, P., Cubaynes, D., Guilbaud, S., Blancard, C., McLaughlin, B. M., & Bizau, J. - M. (2014). Photoionization cross sections of the aluminumlike Si+ ion in the region of the 2p threshold (94-137 eV). PHYSICAL REVIEW A, 90, 063409.
Résumé: We present measurements of the absolute photoionization cross section of the aluminumlike Si+ ion over the 94-137 eV photon energy range. The measurements were performed using the merged-beam setup on the PLEIADES beamline at the SOLEIL synchrotron radiation facility. Signals produced in the Si2+ and Si3+ photoionization channels of the 2p subshell of the Si+ ion from both the 1s(2)2s(2)2p(6)3s(2)3p P-2(1/2,3/2) ground levels and the 1s(2)2s(2)2p(6)3s(3)p(2 4)P metastable levels were observed. Absolute cross sections were determined. Calculations of the 2p inner-shell photoionization cross sections were carried out using the multiconfiguration Dirac-Fock and Dirac-Coulomb R-matrix theoretical approaches and are compared with experiment.
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Kepenekian, M., Gauyacq, J. - P., & Lorente, N. (2014). Difficulties in the ab initio description of electron transport through spin filters. J. Phys. Condens. Matter., 26(10), 104203.
Résumé: Spin-transport calculations present certain difficulties which are sometimes overlooked when using density-functional theory (DFT) to analyze and predict the behavior of molecular-based devices. We analyze and give examples of some caveats of spintronic calculations using DFT. We first describe how the broken-symmetry problem of DFT can cause serious problems in the evaluation of the spin polarization of electron currents. Next, we signal the low-energy scale of magnetic excitations, which makes them ubiquitous at already rather small biases. The existence of excitations in spin transport has catastrophic consequences in the reliability of the usual transport calculations. Finally, we compare DFT and configuration-interaction calculations of a ferrocene-based double decker that has been heralded as a possible spin-filter, and we cast a word of caution when we show that DFT is qualitatively wrong in the description of both the ground state and the excited states of ferrocene double deckers.
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Kossler, S., Feulner, P., & Gauyacq, J. - P. (2014). Electronic excitations of helium bilayers on a metal substrate. Phys. Rev. B, 89(16), 165410.
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Liu, J., Yu, X., Liu, Q., Liu, R., Shang, X., Zhang, S., Li, W., Zheng, W., Zhang, G., Cao, H., & Gu, Z. (2014). Surface-phase junctions of branched TiO2 nanorod arrays for efficient photoelectrochemical water splitting. APPLIED CATALYSIS B-ENVIRONMENTAL, 158, 296–300.
Résumé: Flower-like branched TiO2 nanorod arrays (NRs) owning the surface anatase/rutile junctions on FTO substrates with operational diameter were successfully fabricated by a modified hydrothermal method. Transmission electron microscopy, Raman spectroscopy, field emission scanning electron microscopy, and X-ray diffraction revealed a unique flower-like ranched morphology, surface features, a crystal phase, and lattice constant of TiO2. Photoelectrochemical (PEC) measurements showed excellent photocatalytic properties of the flower-like branched TiO2 NRs. The surface phase formed between anatase and rutile TiO2 NRs which efficiently enhances the separation of photo-generated electron-hole pairs and accelerates the transport of charges is the key influence factor. The results suggest that the branched TiO2 NRs owning the surface anatase/rutile junctions are very promising platform to make highly efficient photoanodes for energy devices. (C) 2014 Elsevier B.V. All rights reserved.
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Ma, Q., Boulet, C., & and Tipping, R. H. (2014). Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules. JOURNAL OF CHEMICAL PHYSICS, 140(24), 244301.
Résumé: The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H2O immersed in N2 bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator −iS1 − S2, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H2O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H2O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H2O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.
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Ma, Q., Boulet, C., & and Tipping, R. H. (2014). Two dimensional symmetric correlation functions of the S operator and two dimensional Fourier transforms: considering the line coupling for P and R lines of linear molecules. JOURNAL OF CHEMICAL PHYSICS, 140(10), 104304.
Résumé: The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys.139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS1 − S2 introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the Sˆ operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters’ two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C2H2 broadened by N2. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements.
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Majumder, M., Sathyamurthy, N., Vazquez, G. J., & Lefebvre-Brion, H. (2014). Interpretation of the accidental predissociation of the E(1) Pi state of CO. J Chem Phys, 140(16), 164303.
Résumé: A special case of predissociation, known as indirect or accidental predissociation observed in the Rydberg E(1)Pi bound state of CO is discussed. We resort to ab initio potentials in order to determine the plausible mechanism for this predissociation. Values of the predissociation width for the valence k(3)Pi state of CO, as obtained from Fermi's golden rule, are also reported. The predissociation width obtained for the mixed E(1)Pi (v = 1, J = 7) state is 0.033 cm(-1) compared to the experimental value of 0.034 cm(-1). The mixed E – E(') state with J = 28, v = 0 is found to be in near resonance condition with the k(3)Pi (v = 4, J = 28) state, thus providing the means to indirect predissociation.
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Mandilara A., Coudreau T., Keller A., & Milman P. (2014). Entanglement classification of pure symmetric states via spin coherent states. Phys. Rev. A, 90, 050302(R).
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Marggi Poullain, S., Elkharrat, C., Li, W. B., Veyrinas, K., Houver, J. C., Cornaggia, C., Rescigno, T. N., Lucchese, R. R., & Dowek, D. (2014). Recoil frame photoemission in multiphoton ionization of small polyatomic molecules: photodynamics of NO2 probed by 400 nm fs pulses. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 47(12), 124024.
Résumé: We report a general method for the complete analysis of the recoil frame photoelectron angular distribution (RFPAD) in n-photon dissociative ionization of small polyatomic molecules, resulting from (n – 1) bound-to-bound transitions plus one-photon ionization of a neutral excited state of the target. This method relies on the decomposition of the RFPAD in terms of the R-K (chi, theta(e)) recoil frame azimuthal harmonics (RFAHs) which are the components of its Fourier expansion in phi(e), where chi and theta(e) are the polar angles referring to the polarization axis P and the photoelectron momentum k relative to the ion fragment recoil direction, respectively, and fe is the azimuth of k relative to P. The RFAH expansion method is illustrated by a detailed experimental and theoretical study of one-colour multiphoton dissociative and non-dissociative ionization of the NO2 molecule of C-2v symmetry induced by 400 nm fs laser pulses, which involve electronic and nuclear dynamics within the pulse duration of the order of 70 fs. The reaction mechanism proposed to account for five-photon dissociative ionization of NO2 involves the role of [R*(6a(1))(-1)] Rydberg states populated by three-photon absorption, subsequently ionized by a fourth photon into the NO2+ (X-1 Sigma(+)(g), upsilon(1),upsilon(2),upsilon(3)) manifold involving autoionization of [R*(4b(2))(-1)] Rydberg states, and linear versus bent geometry selective dissociation of NO2+ (X-1 Sigma(+)(g), upsilon(1),upsilon(2),upsilon(3)) by a fifth photon. The reported calculations provide a coherent picture of the experimental findings although all features are not yet well reproduced.
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Martin-Drumel, M. A., Pirali, O., Falvo, C., Parneix, P., Gamboa, A., Calvo, F., & Brechignac, P. (2014). Low-energy vibrational spectra of flexible diphenyl molecules: biphenyl, diphenylmethane, bibenzyl and 2-, 3-and 4-phenyltoluene. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16(40), 22062–22072.
Résumé: Gas phase absorption far-infrared (FIR) spectra of six flexible hydrocarbon molecules containing two phenyl groups biphenyl, diphenylmethane, bibenzyl and 2-, 3-, 4-phenyltoluene- are reported for the first time, allowing an accurate determination of most of their active low-frequency vibrational modes. DFT calculations have been carried out at the harmonic and perturbative anharmonic levels to predict the vibrational spectra of these molecules and unambiguously assign observed vibrational modes.
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Martin-Drumel, M. A., Pirali, O., & Vervloet, M. (2014). Synchrotron Based FT-FIR Pure Rotational Spectroscopy of the NH2 Radical in Its Two Lowest Vibrational States. JOURNAL OF PHYSICAL CHEMISTRY A, 118(8), 1331–1338.
Résumé: Six Fourier-transform FIR spectra of the NH2 radical have been recorded at high resolution (0.001 cm(-1)) using synchrotron radiation on the AILES beamline at SOLEIL Synchrotron. Three different experimental discharge setups have been used to observe, in absorption, 1009 pure rotational transitions of NH2 in the vibrational ground state (000) and 170 pure rotational transitions within the first excited vibrational state (010). These results constitute a significant extension of the observed quantum numbers for these two states. The spectra permitted several couplings to be resolved (asymmetric coupling, spin-rotation coupling, hyperfine structure) for relatively highly excited energy levels. An effective fit has been realized using both standard Watson-S and -A reductions despite an abnormal centrifugal distortion effect for this light hydride.
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McLaughlin, B. M., Bizau, J. M., Cubaynes, D., Al Shorman, M. M., Guilbaud, S., Sakho, I., Blancard, C., & Gharaibeh, M. F. (2014). K-shell photoionization of B-like oxygen (O3+) ions: experiment and theory. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 47(11), 115201.
Résumé: Absolute cross sections for the K-shell photoionization of boron-like (B-like) O3+ ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron-radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E/Delta E approximate to 5000 (approximate to 110 meV, full width half maximum) was achieved with photon energy from 540 up to 600 eV. Several theoretical approaches, including R-matrix, multi-configuration Dirac-Fock and screening constant by unit nuclear charge were used to identify and characterize the strong 1s -> 2p and the weaker 1s -> 3p resonances observed in the K-shell spectra of this ion. The trend of the integrated oscillator strength and autoionization width (natural line width) of the strong 1s -> 2p resonances along the first few ions of the B-like sequence is discussed.
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Meance, S., Gamby, J., Faure, M., Kou, Q. L., & Haghiri-Gosnet, A. M. (2014). Electrochemiluminescence on-a-chip: Towards a hand-held electrically powered optofluidic source. Talanta, 129, 150–154.
Résumé: We report a microfluidic platform that integrates several parallel optical sources based on electrochemiluminescence (ECL) of 9,10-diphenylanthracene (DPA) as luminophore agent. The annihilation of DPA radicals provides a low wavelength emission at lambda=430 nm in the blue-visible range. By varying the distance between electrodes for each ECL integrated source, this glass/PDMS/glass platform enabled a systematic investigation of the main electrochemical parameters involved in ECL These parameters have been studied either in a static mode or in a dynamic one. Even at slow flow rate (similar to 2 μl s(-1)), the renewal of electroactive species could be easily promoted inside the microfluidic channel which gives rise to a stable optical intensity for several minutes. Compared with traditional optically pumped dye sources, this microfluidic system demonstrates that ECL can be easily implemented on chip for producing much compact optofluidic sources. Such simply electrically powered system-on-chip would surely encourage the future of hand-held μTAS devices with integrated fast detection and embedded electronics. (C) 2014 Elsevier B.V. All rights reserved.
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Meek, S., Poisson, A., Guelachvili, G., Hansch, T. W., & Picque, N. (2014). Fourier transform spectroscopy around 3 μm with a broad difference frequency comb. Applied Physics B-Lasers And Optics, 114(4), 573–578.
Résumé: We characterize a new mid-infrared frequency comb generator based on difference frequency generation around 3.1 μm. High power per comb mode (> 10(-7) W/mode) is obtained over a broad spectral span (> 750 nm, > 790 cm(-1)). The source is used for direct absorption spectroscopy with a Michelson-based Fourier transform interferometer.
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Monsel, A., Lecart, S., Roquilly, A., Broquet, A., Jacqueline, C., Mirault, T., Troude, T., Fontaine-Aupart, M. - P., & Asehnoune, K. (2014). Analysis of Autofluorescence in Polymorphonuclear Neutrophils: A New Tool for Early Infection Diagnosis. PLOS ONE, 9(3), 1790–1800.
Résumé: Diagnosing bacterial infection (BI) remains a challenge for the attending physician. An ex vivo infection model based on human fixed polymorphonuclear neutrophils (PMNs) gives an autofluorescence signal that differs significantly between stimulated and unstimulated cells. We took advantage of this property for use in an in vivo pneumonia mouse model and in patients hospitalized with bacterial pneumonia. A 2-fold decrease was observed in autofluorescence intensity for cytospined PMNs from broncho-alveolar lavage (BAL) in the pneumonia mouse model and a 2.7-fold decrease was observed in patients with pneumonia when compared with control mice or patients without pneumonia, respectively. This optical method provided an autofluorescence mean intensity cut-off, allowing for easy diagnosis of BI. Originally set up on a confocal microscope, the assay was also effective using a standard epifluorescence microscope. Assessing the autofluorescence of PMNs provides a fast, simple, cheap and reliable method optimizing the efficiency and the time needed for early diagnosis of severe infections. Rationalized therapeutic decisions supported by the results from this method can improve the outcome of patients suspected of having an infection.
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Nave, S., Tiwari, A. K., & Jackson, B. (2014). Dissociative chemisorption of methane on Ni and Pt surfaces: mode-specific chemistry and the effects of lattice motion. J Phys Chem A, 118(41), 9615–9631.
Résumé: The dissociative chemisorption of methane on metal surfaces is of great practical and fundamental interest. Not only is it the rate-limiting step in the steam re-forming of natural gas, but also the reaction exhibits interesting mode-specific behavior and a strong dependence on the temperature of the metal. Electronic structure methods are used to explore this reaction on various Ni and Pt surfaces, with a focus on how the transition state is modified by motion of the metal lattice atoms. These results are used to construct models that explain the strong variation in reactivity with substrate temperature, shown to result primarily from changes in the dissociation barrier height with lattice motion. The dynamics of the dissociative chemisorption of CH4 on Ni and Pt is explored, using a fully quantum approach based on the reaction path Hamiltonian that includes all 15 molecular degrees of freedom and the effects of lattice motion. Agreement with experiment is good, and vibrational excitation of the molecule is shown to significantly enhance reactivity. The efficacy for this is examined in terms of the vibrationally nonadiabatic couplings, mode softening, mode symmetry, and energy localization in the reactive bond.
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Ouvrard, A., Wang, J., Ghalgaoui, A., Nave, S., Carrez, S., Zheng, W., Dubost, H., & Bourguignon, B. (2014). CO Adsorption on Pd(100) Revisited by Sum Frequency Generation: Evidence for Two Adsorption Sites in the Compression Stage. J. Phys. Chem. C, 118(34), 19688–19700.
Résumé: Sum frequency generation (SFG) and low-energy electron diffraction (LEED) have been used to revisit CO adsorption on Pd(100) from very low coverages up to saturation at 300 K Below 0.5 ML, variations of SFG frequency and intensity with coverage are consistent with IRAS results from the literature. Novel observations are done above 0.5 ML, where the CO adlayer compression takes place. The existing compression model postulates the coexistence of compressed and uncompressed CO. We observe two bands in the spectral region of bridge sites and assign them to compressed and uncompressed CO. Both types of CO behave very differently: the molecular hyperpolarizability at compressed sites is smaller by a factor of 2 than at uncompressed sites. The frequency of uncompressed CO red-shifts during compression as the partial coverage decreases, while that of compressed CO continues to blue-shift as coverage increases. In the time domain, the coexistence of compressed and uncompressed sites results in oscillations in the decay of SFG intensity. A strong decrease from 690 to 222 fs of the phase relaxation time of uncompressed CO is observed during compression, indicating a stronger coupling to the substrate. These results are complemented by calculations of dipole-dipole interactions and DFT VASP calculations. While continuing blue-shift of compressed sites reflects a combination of increasing dipolar coupling and chemisorption change with coverage like below 0.5 ML, the very large red-shift amplitude of uncompressed CO indicates a large chemical contribution opposite to compressed CO. DFT VASP calculations allow us to follow the surface structure evolution from 0.5 to 0.67 ML and CO frequency changes with coverage. Pd atoms below compressed CO rows are pushed up, and compressed CO is tilted by 8-90 with respect to the surface normal. A frequency split between compressed and uncompressed CO is found in agreement with experimental data. These results suggest that while compressed CO is less strongly bonded as compression proceeds the remaining uncompressed CO is more strongly bonded.
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Pasquali, L., Mukherjee, S., Terzi, F., Giglia, A., Mahne, N., Koshmak, K., Esaulov, V., Toccafondi, C., Canepa, M., & Nannarone, S. (2014). Structural and electronic properties of anisotropic ultrathin organic films from dichroic resonant soft x-ray reflectivity. Phys. Rev. B, 89(4), 045401.
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Perez-Torres, J. F., Sanz-Vicario, J. L., Veyrinas, K., Billaud, P., Picard, Y. J., Elkharrat, C., Marggi Poullain, S., Saquet, N., Lebech, M., Houver, J. C., Martin, F., & Dowek, D. (2014). Circular dichroism in molecular-frame photoelectron angular distributions in the dissociative photoionization of H-2 and D-2 molecules. PHYSICAL REVIEW A, 90(4), 043417.
Résumé: The presence of net circular dichroism in the photoionization of nonchiral homonuclear molecules has been put in evidence recently through the measurement of molecular-frame photoelectron angular distributions in dissociative photoionization of H-2 [Dowek et al., Phys. Rev. Lett. 104, 233003 (2010)]. In this work we present a detailed study of circular dichroism in the photoelectron angular distributions of H-2 and D-2 molecules, oriented perpendicularly to the propagation vector of the circularly polarized light, at different photon energies (20, 27, and 32.5 eV). Circular dichroism in the angular distributions at 20 and to a large extent 27 eV exhibits the usual pattern in which inversion symmetry is preserved. In contrast, at 32.5 eV, the inversion symmetry breaks down, which eventually leads to total circular dichroism after integration over the polar emission angle. Time-dependent ab initio calculations support and explain the observed results for H-2 in terms of quantum interferences between direct photoionization and delayed autoionization from the Q(1) and Q(2) doubly excited states into ionic states (1s sigma(g) and 2p sigma(u)) of different inversion symmetry. Nevertheless, for D-2 at 32.5 eV, there is a particular case where theory and experiment disagree in the magnitude of the symmetry breaking: when D+ ions are produced with an energy of around 5 eV. This reflects the subleties associated to such simple molecules when exposed to this fine scrutiny.
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Picard, Y. J., Manschwetus, B., Geleoc, M., Bottcher, M., Casagrande, E. M. S., Lin, N., Ruchon, T., Carre, B., Hergott, J. F., Lepetit, F., Taieb, R., Maquet, A., & Huetz, A. (2014). Attosecond evolution of energy- and angle-resolved photoemission spectra in two-color (XUV plus IR) ionization of rare gases. Physical Review A, 89(3), 031401.
Résumé: We have analyzed the angular distributions of the photoelectrons emitted upon photoionization of rare gases by a comb of harmonics in the extreme ultraviolet range, in the presence of a “dressing” infrared (IR) field with controlled delay tau, stabilized down to about +/-60 as. The measurements have been performed with the help of the coincidence momentum imaging technique. We evidence marked differences in the measured angular distributions of the photoelectrons, depending on the number of IR photons exchanged. Joined to a theoretical interpretation, these observations bring new insights into the dynamics of this class of two-color photoionization processes that are a key step towards studying photoionization in the time domain, with attosecond time resolution.
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Piekarczyk, A., Bald, I., Flosadóttir, H. D., Ómarsson, B., Lafosse, A., & Ingólfsson, O. (2014). Influence of metal ion complexation on the metastable fragmentation of DNA hexamers. Eur. Phys. J. D, 68(6), 146.
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Pirali, O., Boudon, V., Carrasco, N., & Dartois, E. (2014). Rotationally resolved IR spectroscopy of hexamethylenetetramine (HMT) C6N4H12. ASTRONOMY & ASTROPHYSICS, 561, A109.
Résumé: Context. Hexamethylenetetramine (HMT) appears to be a potential constituent of several objects in space, including comets or Titan's atmosphere and, as an organic residue of ice irradiation in the laboratory, it may be present in the interstellar medium.
Aims. We performed a laboratory study of rotationally resolved intense IR bands of HMT to provide accurate line positions and synthetic spectra to be used for potential astronomical detections.
Methods. We used synchrotron-based high-resolution Fourier transform infrared spectroscopy to record the experimental data. A formalism and programs dedicated to the assignment, analysis, and simulation of absorption spectra of tetrahedral molecules were used to exploit the spectra.
Results. Infrared spectra of gas phase HMT were recorded and accurate wavenumbers and molecular parameters for four intense bands located in the 1000-1500 cm(-1) spectral range suitable for astronomical searches were derived.
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Porcel, E., Tillement, O., Lux, F., Mowat, P., Usami, N., Kobayashi, K., Furusawa, Y., Le Sech, C., Li, S., & Lacombe, S. (2014). Gadolinium-based nanoparticles to improve the hadrontherapy performances. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE, 10(8), 1601–1608.
Résumé: Nanomedicine is proposed as a novel strategy to improve the performance of radiotherapy. High-Z nanoparticles are known to enhance the effects of ionizing radiation. Recently, multimodal nanoparticles such as gadolinium-based nanoagents were proposed to amplify the effects of x-rays and g-rays and to improve MRI diagnosis. For tumors sited in sensitive tissues, childhood cases and radioresistant cancers, hadrontherapy is considered superior to x-rays and g-rays. Hadrontherapy, based on fast ion radiation, has the advantage of avoiding damage to the tissues behind the tumor; however, the damage caused in front of the tumor is its major limitation. Here, we demonstrate that multimodal gadolinium-based nanoparticles amplify cell death with fast ions used as radiation. Molecular scale experiments give insights into the mechanisms underlying the amplification of radiation effects. This proof-of-concept opens up novel perspectives for multimodal nanomedicine in hadrontherapy, ultimately reducing negative radiation effects in healthy tissues in front of the tumor. From the Clinical Editor: Gadolinium-chelating polysiloxane nanoparticles were previously reported to amplify the anti-tumor effects of x-rays and g-rays and to serve as MRI contrast agents. Fast ion radiation-based hadrontherapy avoids damage to the tissues behind the tumor, with a major limitation of tissue damage in front of the tumor. This study demonstrates a potential role for the above nanoagents in optimizing hadrontherapy with preventive effects in healthy tissue and amplified cell death in the tumor. (C) 2014 Elsevier Inc. All rights reserved.
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Puthumpally-Joseph, R., Sukharev, M., Atabek, O., & Charron, E. (2014). Dipole-Induced Electromagnetic Transparency. Phys. Rev. Lett., 113, 163603.
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Quirico, E., Orthous-Daunay, F. - R., Beck, P., Bonal, L., Brunetto, R., Dartois, E., Pino, T., Montagnac, G., Rouzaud, J. - N., Engrand, C., & Duprat, J. (2014). Origin of insoluble organic matter in type 1 and 2 chondrites: New clues, new questions. GEOCHIMICA ET COSMOCHIMICA ACTA, 136, 80–99.
Résumé: Insoluble organic matter (IOM) extracted from primitive chondrites is a polyaromatic solid with a structure and composition resembling that of terrestrial kerogens. A survey of its composition and structure has been carried out on a series of 27 CR, CM, CI and ungrouped C2 carbonaceous chondrites (Tagish Lake, Bells, Essebi, Acfer 094) using infrared and multi-wavelength Raman micro-spectroscopy (244, 514 and 785 nm laser excitations). The results show that chondritic IOM from PCA 91008 (CM2), WIS 91600 (CM2), QUE 93005 (CM2), Tagish Lake (C2 ungrouped) and possibly Cold Bokkeveld (CM2) has been subjected to the past action of short duration thermal metamorphism, presumably triggered by impacts. The IOM in most of the CM chondrites that experienced moderate to heavy aqueous alteration may have been slightly modified by collision-induced heating. However, even IOM from chondrites that escaped significant thermal metamorphism displays Raman characteristics consistent with a formation by thermal processing, either in the protosolar disk or in the parent body. An alternative energetic process to thermal heating is ion irradiation. After thoroughly analyzing both these scenarii, no conclusion can be drawn as to which is the most plausible mechanism nor whether the heating process took place prior or after accretion. The results show for the first time that the width of the G band in spectra collected with a 514 nm excitation correlates with the O/C atomic ratio, suggesting a major role of oxygen in the cross-linking of polyaromatic units.
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Quoilin, C., Mouithys-Mickalad, A., Lecart, S., Fontaine-Aupart, M. - P., & Hoebeke, M. (2014). Evidence of oxidative stress and mitochondrial respiratory chain dysfunction in an in vitro model of sepsis-induced kidney injury. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1837(10), 1790–1800.
Résumé: To investigate the role of oxidative stress and/or mitochondrial impairment in the occurrence of acute kidney injury (AKI) during sepsis, we developed a sepsis-induced in vitro model using proximal tubular epithelial cells exposed to a bacteria] endotoxin (lipopolysaccharide, LPS). This investigation has provided key features on the relationship between oxidative stress and mitochondrial respiratory chain activity defects. LPS treatment resulted in an increase in the expression of inducible nitric oxide synthase (iNOS) and NADPH oxidase 4 (NOX-4), suggesting the cytosolic overexpression of nitric oxide and superoxide anion, the primary reactive nitrogen species (RNS) and reactive oxygen species (ROS). This oxidant state seemed to interrupt mitochondrial oxidative phosphorylation by reducing cytochrome c oxidase activity. As a consequence, disruptions in the electron transport and the proton pumping across the mitochondrial inner membrane occurred, leading to a decrease of the mitochondrial membrane potential, a release of apoptotic-inducing factors and a depletion of adenosine triphosphate. Interestingly, after being targeted by RNS and ROS, mitochondria became in turn producer of ROS, thus contributing to increase the mitochondrial dysfunction. The role of oxidants in mitochondrial dysfunction was further confirmed by the use of iNOS inhibitors or antioxidants that preserve cytochrome c oxidase activity and prevent mitochondria] membrane potential dissipation. These results suggest that sepsis-induced AKI should not only be regarded as failure of energy status but also as an integrated response, including transcriptional events, ROS signaling, mitochondrial activity and metabolic orientation such as apoptosis. (C) 2014 Elsevier B.V. All rights reserved.
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Ralay-Ranaivo, B., Desmaele, D., Bianchini, E. P., Lepeltier, E., Bourgaux, C., Borgel, D., Pouget, T., Tranchant, J. F., Couvreur, P., & Gref, R. (2014). Novel self assembling nanoparticles for the oral administration of fondaparinux: Synthesis, characterization and in vivo evaluation. Journal Of Controlled Release, 194, 323–331.
Résumé: Fondaparinux (Fpx) is the anticoagulant of choice in the treatment of short- and medium-term thromboembolic disease. To overcome the low oral bioavailability of Fpx, a new nanoparticulate carrier has been developed. The nanoparticles (NPs) contain squalenyl derivatives, known for their excellent oral bioavailability. They spontaneously self-assemble upon both electrostatic and hydrophobic interactions between the polyanionic Fpx and cationic squalenyl (CSq) derivatives. The preparation conditions were optimized to obtain monodisperse, stable NPs with a mean diameter in the range of 150-200 nm. The encapsulation efficiencies were around 80%. Fpx loadings reached 39 wt.%. According to structural and morphological analysis, Fpx and CSq organized in spherical multilamellar (“onion-type”) nanoparticles. Furthermore, in vivo studies in rats suggested that Fpx was well absorbed from the orally administered NPs, which totally dissociated when reaching the blood stream, leading to the release of free Fpx. The Fpx: CSq NPs improved the plasmatic concentration of Fpx in a dose-dependent manner. However, the oral bioavailability of these new NPs remained low (around 0.3%) but of note, the C-max obtained after oral administration of 50 mg/kg NPs was close to the prophylactic plasma concentration needed to treat venous thromboembolism. Moreover, the oral bioavailability of Fpx could be dramatically increased up to 9% by including the nanoparticles into gastroresistant capsules. This study opens up new perspectives for the oral administration of Fpx and paves the way towards elaborating squalene-based NPs which self assemble without the need of covalently grafting the drug to Sq. (C) 2014 The Authors. Published by Elsevier B.V.
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Rampazzo, E., Bonacchi, S., Genovese, D., Juris, R., Montalti, M., Paterlini, V., Zaccheroni, N., Dumas-Verdes, C., Clavier, G., Meallet-Renault, R., & Prodi, L. (2014). Pluronic-Silica (PluS) Nanoparticles Doped with Multiple Dyes Featuring Complete Energy Transfer. Journal Of Physical Chemistry C, 118(17), 9261–9267.
Résumé: We report here the design of two sets Of multifltiorophoric silica nanoparticles, observing unprecedented efficiencies in the energy-transfer processes among the doping dyes. These nanomaterials show a very high overall sensitization, allowing under a single wavelength excitation to obtain many different colors (one per nanoparticle) in emission with negligible crosstalk. Moreover, each particle can present very large and tunable pseudo-Stokes shifts (up to 435 nm), a very high brightness even exciting the bluest donor, and a negligible residual emission intensity from all donor dyes. All these features, combined with colloidal stability and synthetic method reliability, make these multicomponent nanoparticles very promising for multiplex analysis and for all the diagnostic techniques requiring high sensitivity associated with a large Stokes shift.
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Rogez, B., Yang, H., Le Moal, E., Lévêque-Fort, S., Boer-Duchemin, E., Yao, F., Lee, Y. - H., Zhang, Y., Wegner, D., Hildebrandt, N., Mayne, A. J., & Dujardin G. (2014). Fluorescence lifetime and blinking of individual semiconductor nanocrystals on graphene. J. Phys. Chem. C, 118, 18445–18452.
Résumé: A new class of optoelectronic nanodevices consisting of 0D semiconductor nanocrystals and 2D single graphene layers is attracting much attention. In particular, such a system may be used to investigate and control the transfer of energy and charge in low-dimensional systems. To this end, the fluorescence dynamics of individual colloidal quantum dots(QDs) on graphene are investigated on both the 10−9 to 10−8 s time scale (fluorescence lifetime) and the 1−100 s time scale(blinking statistics) in this paper. We find that (i) a nonradiative energy transfer rate of ≈5 × 10+8 s−1 is obtained from the reduced lifetimes of QDs on graphene as opposed to those on insulating substrates such as glass; (ii) QDs still exhibit fluorescence intermittency (“blinking”) on graphene; (iii) the cumulative distribution functions of the “off” times may be described by power-law statistics; (iv) QD coupling to graphene increases the time spent in the “on” state while the time spent in the “off” state remains relatively unchanged; and (v) the fluorescence emission spectrum of the QDs is practically unaltered by the QD−graphene coupling.
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Rousselot, P., Pirali, O., Jehin, E., Vervloet, M., Hutsemekers, D., Manfroid, J., Cordier, D., Martin-Drumel, M. - A., Gruet, S., Arpigny, C., Decock, A., & Mousis, O. (2014). Toward a unique nitrogen isotopic ratio in cometary ices. ASTROPHYSICAL JOURNAL LETTERS, 780(2), L17.
Résumé: Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in comets due to the (NH2)-N-15 radical produced by the photodissociation of (NH3)-N-15. Analysis of our data has permitted us to measure the N-14/N-15 isotopic ratio in comets for a molecule carrying the amine (-NH) functional group. This ratio, within the error, appears similar to that measured in comets in the HCN molecule and the CN radical, and lower than the protosolar value, suggesting that N-2 and NH3 result from the separation of nitrogen into two distinct reservoirs in the solar nebula. This ratio also appears similar to that measured in Titan's atmospheric N-2, supporting the hypothesis that, if the latter is representative of its primordial value in NH3, these bodies were assembled from building blocks sharing a common formation location.
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Sancey, L., Lux, F., Kotb, S., Roux, S., Dufort, S., Bianchi, A., Cremillieux, Y., Fries, P., Coll, J. - L., Rodriguez-Lafrasse, C., Janier, M., Dutreix, M., Barberi-Heyob, M., Boschetti, F., Denat, F., Louis, C., Porcel, E., Lacombe, S., Le Duc, G., Deutsch, E., Perfettini, J. - L., Detappe, A., Verry, C., Berbeco, R., Butterworth, K. T., McMahon, S. J., Prise, K. M., Perriat, P., & Tillement, O. (2014). The use of theranostic gadolinium-based nanoprobes to improve radiotherapy efficacy. The British journal of radiology, 87(1041).
Résumé: A new efficient type of gadolinium-based theranostic agent (AGuIX) has recently been developed for MRI-guided radiotherapy (RT). These new particles consist of a polysiloxane network surrounded by a number of gadolinium chelates, usually 10. Owing to their small size (<5nm), AGuIX typically exhibit biodistributions that are almost ideal for diagnostic and therapeutic purposes. For example, although a significant proportion of these particles accumulate in tumours, the remainder is rapidly eliminated by the renal route. In addition, in the absence of irradiation, the nanoparticles are well tolerated even at very high dose (10 times more than the dose used for mouse treatment). AGuIX particles have been proven to act as efficient radiosensitizers in a large variety of experimental in vitro scenarios, including different radioresistant cell lines, irradiation energies and radiation sources (sensitizing enhancement ratio ranging from 1.1 to 2.5). Pre-clinical studies have also demonstrated the impact of these particles on different heterotopic and orthotopic tumours, with both intratumoural or intravenous injection routes. A significant therapeutical effect has been observed in all contexts. Furthermore, MRI monitoring was proven to efficiently aid in determining a RT protocol and assessing tumour evolution following treatment. The usual theoretical models, based on energy attenuation and macroscopic dose enhancement, cannot account for all the results that have been obtained. Only theoretical models, which take into account the Auger electron cascades that occur between the different atoms constituting the particle and the related high radical concentrations in the vicinity of the particle, provide an explanation for the complex cell damage and death observed.
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Scuderi, D., Lepere, V., Piani, G., Bouchet, A., & Zehnacker-Rentien, A. (2014). Structural Characterization of the UV-Induced Fragmentation Products in an Ion Trap by Infrared Multiple Photon Dissociation Spectroscopy. JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5(1), 56–61.
Résumé: Protonated cinchona alkaloids and their dimers undergo photochemical reaction in the gas phase, leading to UV-specific photofragments, not observed by collision-induced dissociation. Simultaneous coupling of UV and IR lasers with a Paul ion trap has been achieved for obtaining the vibrational spectrum of the fragments arising from the photodissociation. The structure of the photoproduced radical has been fully characterized by comparing the experimental spectrum to that simulated by DFT calculations.
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Shafizadeh, N., Ha-Thi, M. - H., Poisson, L., Soep, B., & Maillard, P. (2014). Observation in the gas phase of the ligation of 1-Methylimidazole to hemoprotein mimics. JOURNAL OF CHEMICAL PHYSICS, 141(17), 174310.
Résumé: Hemoprotein mimics, cobalt picket fence porphyrins have been prepared in the gas phase as neutral molecules for the first time. Their ligation properties have been studied with 1-methylimidazole and compared with those of other cobalt porphyrins, tetraphenyl porphyrin, and cobalt protoporphyrin IX chloride, in view of studying the sterical properties of the ligation. It is shown that the cobalt picket fence porphyrin can only accept one 1-methylimidazole ligand in contrast to less sterically crowded porphyrins like cobalt tetraphenylporphyrin that present two accessible ligation sites. The femtosecond dynamics of these ligated systems have been studied after excitation at 400 nm, in comparison with the unligated ones. The observed transients are formed in much shorter times, 30 fs for the ligated species, as compared to free species (100 fs), supporting the porphyrin to metal charge transfer nature of these transients. The similar decays of the ligated transients <1 ps reveal the absence of photodissociation of the cobalt-1-methylimidazole bond at this step of evolution.
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Sivankutty, S., Barroca, T., Mayet, C., Dupuis, G., Fort, E., & Leveque-Fort, S. (2014). Confocal supercritical angle microscopy for cell membrane imaging. Opt Lett, 39(3), 555–558.
Résumé: We demonstrate subwavelength sectioning on biological samples with a conventional confocal microscope. This optical sectioning is achieved by the phenomenon of supercritical angle fluorescence, wherein only a fluorophore next to the interface of a refractive index discontinuity can emit propagating components of radiation into the so-called forbidden angles. The simplicity of this technique allows it to be integrated with a high numerical aperture confocal scanning microscope by only a simple modification on the detection channel. Confocal-supercritical angular fluorescence microscopy would be a powerful tool to achieve high-resolution surface imaging, especially for membrane imaging in biological samples.
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Sohn, W. Y., Ishiuchi, S., Carcabal, P., Oba, H., & Fujii, M. (2014). UV-UV hole burning and IR dip spectroscopy of homophenylalanine by laser desorption supersonic jet technique. Chemical Physics, 445, 21–30.
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Soorkia, S., Broquier, M., & Grégoire, G. (2014). Conformer- and Mode-Specific Excited State Lifetimes of Cold Protonated Tyrosine Ions. J. Phys. Chem. Lett., 5(24), 4349–4355.
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Soorkia, S., Dehon, C., Kumar, S. S., Pedrazzani, M., Frantzen, E., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2014). UV Photofragmentation Dynamics of Protonated Cystine: Disulfide Bond Rupture. J Phys Chem Lett, 5(7), 1110–1116.
Résumé: Disulfide bonds (S-S) play a central role in stabilizing the native structure of proteins against denaturation. Experimentally, identification of these linkages in peptide and protein structure characterization remains challenging. UV photodissociation (UVPD) can be a valuable tool in identifying disulfide linkages. Here, the S-S bond acts as a UV chromophore and absorption of one UV photon corresponds to a sigma-sigma* transition. We have investigated the photodissociation dynamics of protonated cystine, which is a dimer of two cysteines linked by a disulfide bridge, at 263 nm (4.7 eV) using a multicoincidence technique in which fragments coming from the same fragmentation event are detected. Two types of bond cleavages are observed corresponding to the disulfide (S-S) and adjacent C-S bond ruptures. We show that the S-S cleavage leads to three different fragment ions via three different fragmentation mechanisms. The UVPD results are compared to collision-induced dissociation (CID) and electron-induced dissociation (EID) studies.
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Štefančíková L., P. E., Eustache P., Li S., Salado D., Marco S., Guerquin-Kern J.L., Réfrégiers M., Tillement O., Lux F., and Lacombe S. (2014). Cell localisation of gadolinium-based nanoparticles and related radiosensitising efficacy in glioblastoma cells. Cancer Nanotechnology. Cancer Nanotechnology, 5(1), 6.
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Sugny, D., Vranckx, S., Ndong, M., Vaeck, N., Atabek, O., & Desouter-Lecomte, M. (2014). Control of molecular dynamics with zero-area fields: Application to molecular orientation and photofragmentation. Physical Review A, 90, 053404.
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Tarakeshwar P., Palma J. L., Finkelstein-Shapiro D., Keller A., Urdaneta I., Calatayud M., Atabek O., & Mujica V. (2014). SERS as a probe of charge-transfer pathways in hybrid dye/molecule-metal oxide complexes. J. Phys. Chem. C, 118, 3774.
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Tchalala, M. R., Enriquez, H., Yildirim, H., Kara, A., Mayne, A. J., Dujardin, G., Ali, M. A., & Oughaddou, H. (2014). Atomic and electronic structures of the (root 13 x root 13)R13.9 degrees of silicene sheet on Ag(111). APPLIED SURFACE SCIENCE, 303, 61–66.
Résumé: Using scanning tunneling microscopy, low energy electron diffraction measurements, and ab initio calculations based on density functional theory, we present atomic models of the (root 13 x root 13)R13.9 degrees silicene superstructure grown on Ag(1 1 1). The STM images reveal two co-existing atomic arrangements with two different orientations of the silicene sheet relative to the Ag(1 1 1) surface. DFT calculations with and without the inclusion of van der Waals interactions show corrugated Si atomic positions for both orientations implying a significant interaction with Ag(1 1 1) surface. The electronic structure of both silicene and Ag(1 1 1) surface are sufficiently affected that new interface states emerge close to the Fermi level. (C) 2014 Elsevier B.V. All rights reserved.
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Thibault, F., Ma Q., & and Boulet, C. (2014). Line coupling effects in the isotropic Raman spectra of N2: A quantum calculation at room temperature. JOURNAL OF CHEMICAL PHYSICS, 140(4), 044303.
Résumé: We present quantum calculations of the relaxation matrix for the Q branch of N2 at room temperature using a recently proposed N2-N2 rigid rotor potential. Close coupling calculations were complemented by coupled states studies at high energies and provide about 10 200 two-body state-to state cross sections from which the needed one-body cross-sections may be obtained. For such temperatures, convergence has to be thoroughly analyzed since such conditions are close to the limit of current computational feasibility. This has been done using complementary calculations based on the energy corrected sudden formalism. Agreement of these quantum predictions with experimental data is good, but the main goal of this work is to provide a benchmark relaxation matrix for testing more approximate methods which remain of a great utility for complex molecular systems at room (and higher) temperatures.
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Urdaneta I., Keller A., Atabek O., Palma J. L., Finkelstein-Shapiro D., Tarakeshwar P., Mujica V., & Calatayud M. (2014). Dopamine Adsorption on TiO2 Anatase Surfaces. J. Phys. Chem. C, 118, 20688.
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Urdaneta I., Pilmé J., Keller A., Atabek O., Tarakeshwar P., Mujica V., & Calatayud M. (2014). Probing Raman enhancement in Dopamine-Ti2O4 hybrid using stretched molecular geometries. J. Phys. Chem. A, 118, 1196.
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Vernaz-Gris P., Ketterer A., Keller A., Walborn S. P., Coudreau T., & Milman P. (2014). Continuous discretization of in nite-dimensional Hilbert spaces. Phys. Rev. A, 89, 052311.
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Wang, J., Dubost, H., Ghalgaoui, A., Zheng, W., Carrez, S., Ouvrard, A., & Bourguignon, B. (2014). Effect of visible pulse shaping on the accuracy of relative intensity measurements in BBSFG vibrational spectroscopy. Surf. Sci., 626, 26–39.
Résumé: Quantitative analysis of BroadBand Sum Frequency Generation (BBSFG) vibrational spectra by deconvolution into Lorentzian components has been shown recently to suffer from complications that depend on the spectrotemporal properties and delay of the visible pulse which has to be shaped in order to achieve spectral resolution and possibly temporal discrimination. We present a comprehensive spectro-temporal analysis of BBSFG in order to evaluate quantitatively the consequences of delay dependent spectral changes on the accuracy of BBSFG spectra. We compare purely spectral deconvolution of single spectra and spectro-temporal analysis of multiple spectra obtained with a picosecond visible pulse produced by either a Fabry-Perot (FP) etalon or a 4f pulse shaper (PS). The case of OctaDecaneThiol Self Assembled Monolayer is used for comparison of theory and experiment. Accurate relative intensities can only be obtained from the analysis of multiple spectra generated by the FP-produced visible pulse. Although the spectra obtained with the PS are not delay dependent contrarily to those of the FP, the purely spectral deconvolution does not provide accurate values of the relative intensities. The need for a spectro-temporal analysis is explained by the fact that the first-order IR polarization is distorted both in the time domain by the ps visible pulse shape and in the frequency domain by interferences between the bands that are complicated by a frequency and delay dependent phase shift (C) 2014 Elsevier B.V. All rights reserved.
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Wang, T., Boer-Duchemin, E., Comtet, G., Le Moal, E., Dujardin, G., Drezet, A., & Huant, S. (2014). Plasmon scattering from holes: from single hole scattering to Young's experiment. Nanotechnology, 25(12), 125202.
Résumé: In this paper, the scattering of surface plasmon polaritons (SPPs) into photons at holes is investigated. A local, electrically excited source of SPPs using a scanning tunneling microscope (STM) produces an outgoing circular plasmon wave on a thick (200 nm) gold film on glass containing holes of 250, 500 and 1000 nm diameter. Fourier plane images of the photons from hole-scattered plasmons show that the larger the hole diameter, the more directional the scattered radiation. These results are confirmed by a model where the hole is considered as a distribution of horizontal dipoles whose relative amplitudes, directions, and phases depend linearly on the local SPP electric field. An SPP-Young's experiment is also performed, where the STM-excited SPP wave is incident on a pair of 1 μm diameter holes in the thick gold film. The visibility of the resulting fringes in the Fourier plane is analyzed to show that the polarization of the electric field is maintained when SPPs scatter into photons. From this SPP-Young's experiment, an upper bound of approximate to 200 nm for the radius of this STM-excited source of surface plasmon polaritons is determined.
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Wang, T., Comtet, G., Le Moal, E., Dujardin, G., Drezet, A., Huant, S. & Boer-Duchemin, E. (2014). Temporal coherence of propagating surface plasmons. Opt. Lett., 39(23), 6679–6682.
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Wardé, M., Ledieu, J., Serkovic Loli, L. N., Herinx, M., de Weerd, M. - C., Fournée, V., Le Moal, S., & Barthés-Labrousse, M. G. (2014). Growth and structure of ultrathin aluminafilms on the (110) surface of γ-Al4Cu9 complex metallic alloy. JOURNAL OF PHYSICS-CONDENSED MATTER, 26, 485009.
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Yang, H., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., Nagarajan, S., & Gourdon, A. (2014). Single-molecule light emission at room temperature on a wide-band-gap semiconductor. Phys. Rev. B, 90(12), 125427.
Résumé: Room-temperature light emission from single chemisorbed perylene based molecules adsorbed on silicon carbide (SiC) is probed by a scanning tunneling microscopy. A new approach to STM-induced luminescence of a single molecule is explored using a wide band gap semiconductor to decouple electronically the molecule from the surface. After molecular adsorption, the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) both lie within the bulk band gap and below the Fermi level of the substrate. The maximum photon energy of the light emission from the molecule shows a fixed shift of 1.5 eV relative to the maximum energy of the tunnel electrons. This is consistent with the photons being generated by inelastic electron tunneling between the highest occupied molecular orbital and the unoccupied electronic states of the STM tip.
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Yengui, M., & Riedel, D. (2014). Cobalt adsorption on the bare Si(100)-2x1 surface at low temperature (12 K). SURFACE SCIENCE, 619(1), 10–18.
Résumé: The adsorption of Co atoms on the bare Si(100)-2×1 surface at low temperature (12 K) is performed in the low coverage regime (b 0.1monolayer). The ensuing surface is studied by means of a lowtemperature (9K) scanning tunneling microscope (STM). Several adsorption sites are described via STM topographies and differential conductance spectroscopy. Our study reveals that at low temperature (12 K), a significant fraction of the Co atoms diffuse into the surface and form the first stage reaction sites that are relevant for the silicidation mechanism of the Si(100). Furthermore, the low temperature conditions allow to describe surface Co adatoms conformations that are stabilized on the Si(100)-c(4×2) surface. Interestingly,we have observed the irreversible transformation of the symmetric pedestal site (Ps) to the under dimer site (UD) via specific STM scanning conditions. Finally, the presence of dimer vacancy lines is discussed and reveals that the activated etching process of the silicon dimer with metals can be induced at very low temperature.
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Zehnacker, A. (2014). Chirality effects in gas-phase spectroscopy and photophysics of molecular and ionic complexes: contribution of low and room temperature studies. INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY, 33(2), 151–207.
Résumé: This review focuses on chirality effects in spectroscopy and photophysics of chiral molecules or protonated ions, and their weakly bound complexes, isolated in the gas phase. Low-temperature studies in jet-cooled conditions allow disentangling the different interactions at play and shed light on the ancillary interactions responsible for chiral recognition, like OH...pi or CH...pi, which would be blurred at room temperature. The consequences of these interactions on chiral recognition in condensed phase are described, as well as the influence of higher energy conformers, which can be accessed in room-temperature experiments. The role of kinetic effects and solvation in jet-cooled experiments is discussed. Last, examples of dramatic chirality effects in photo-induced dissociation are given.
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Actes de Conférences |
Bocchetti, V., Diep, H. T., Enriquez, H., Oughaddou, H., & Kara, A. (2014). Thermal stability of standalone silicene sheet. In JOURNAL OF PHYSICS-CONFERENCE SERIES (Vol. 491, 012008). 3RD INTERNATIONAL MEETING ON SILICENE (IMS-3).
Résumé: Extensive Monte Carlo simulations are carried out to study thermal stability of an infinite standalone silicon sheet. We used the Tersoff potential that has been used with success for silicon at low temperatures. However, the melting temperature T-m calculated with the original parameters provided by Tersoff is too high with respect to the experimental one. Agrawal, Raff and Komanduri have proposed a modified set of parameters to reduce T-m. For comparison, we have used these two sets of parameters to study the stability and the melting of a standalone 2D sheet of silicon called “silicene”, by analogy with graphene for the carbon sheet. We find that 2D crystalline silicene is stable up to a high temperature unlike in 2D systems with isotropic potentials such as Lennard-Jones. The differences in the obtained results using two sets of parameters are striking.
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Boer-Duchemin, E., Wang, T., Le Moal, E., Rogez, B., Comtet, G., & Dujardin, G. (2014). Local, low energy, electrical excitation of localized and propagating surface plasmons with a scanning tunneling microscope. In Proceeding of the SPIE (Vol. 9126, 91260K). Nanophysics V.
Résumé: The highly confined nature of the fields from surface plasmons makes them excellent candidates for future nano-optical devices. Most often, optical excitation is used to excite surface plasmons. However, a local, low energy, electrical method for surface plasmon excitation would be preferable for device applications.
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Calisti, A., Ferri, S., Mosse, C., Talin, B., Klisnick, A., Meng, L., Benredjem, D., & Guilbaud, O. (2014). Study of Particle Correlation Effects on Line Profiles of Ni-Like Collisional XUV Laser Amplifier. In X-RAY LASERS 2012 (Vol. 147, pp. 49–53).
Résumé: We discuss the effects of particle correlations on the spectral broadening due to the radiator motion (Doppler broadening) for a Ni-like XUV laser line pumped in two different regimes (transient and quasi-steady state regimes) of collisional excitation. In a medium with gain, radiative transport effects modify the observed profile and these modifications depend on the homogeneous or inhomogeneous nature of the intrinsic profile (before amplification). The intrinsic line profile is usually described by a Voigt profile, which is the convolution of a Lorentzian profile due to the different homogeneous broadenings (electron collision-induced transitions and spontaneous emission) and an inhomogeneous Gaussian profile due to Doppler shifts (due to the radiator motion in the free-particle limit). In this paper, it is shown that accounting for the correlations between particles modifies noticeably the radiator-motion broadened profiles, whatever the densities and temperatures values.
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Chen, L., & Esaulov, V. A. (2014). Energy loss of keV ions in grazing scattering on gold surfaces. In JOURNAL OF PHYSICS-CONFERENCE SERIES (Vol. 488, 132016).
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Enriquez, H., Kara, A., Mayne, A. J., Dujardin, G., Jamgotchian, H., Aufray, B., & Oughaddou, H. (2014). Atomic structure of the (2 root 3 x 2 root 3)R30 degrees of silicene on Ag(111) surface. In JOURNAL OF PHYSICS-CONFERENCE SERIES (Vol. 491, 012004). 3RD INTERNATIONAL MEETING ON SILICENE (IMS-3).
Résumé: The deposition of one monolayer of silicon on a Ag(111) substrate induces the formation of silicene structures exhibiting different ordered phases, including a (2 root 3x2 root 3)R30 degrees, a (4 x 4) and a (root 13x root 13)R13.9 degrees superstructures. In this paper we focus on the (2 root 3x root 3)R30 degrees phase. Using a combination of scanning tunneling microscopy and LEED observations, we show that this phase corresponds to a 11 degrees rotation of the silicene sheet relative to the substrate orientation.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Hansch, T. W., & Picque, N. (2014). Coherent Raman dual-comb spectroscopy and imaging. In Real-Time Photonic Measurements (Vol. 9279).
Résumé: The invention of the optical frequency comb technique has revolutionized the field of precision spectroscopy, providing a way to measure the absolute frequency of any optical transition. Since, frequency combs have become common equipment for frequency metrology. In the last decade, novel applications for the optical frequency comb have been demonstrated beyond its original purpose. Broadband molecular spectroscopy is one of those. One such technique of molecular spectroscopy with frequency combs, dual-comb Fourier transform spectroscopy provides short measurement times with resolution and accuracy. Two laser frequency combs with slightly different repetition frequencies generate pairs of pulses with a linearly-scanned delay between pulses in a pair. The system without moving parts mimics a fast scanning Fourier transform interferometer. The measurement speed may be several orders of magnitude faster than that of a Michelson-based Fourier transform spectrometer, which opens up new opportunities for broadband molecular spectroscopy. Recently, dual-comb spectroscopy has been extended to nonlinear phenomena. A broadband Raman spectrum of molecular fingerprints may be measured within a few tens of microseconds with coherent Raman dual-comb spectroscopy. Raster scanning the sample leads to hyperspectral images. This rapid and broadband label-free vibrational spectroscopy and imaging technique might provide new diagnostic methods in a variety of scientific and industrial fields.
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Kozlova, M., Nejdl, J., Krus, M., Prokupek, J., Dostal, J., Rus, B., Klisnick, A., Meng, L., Tissandier, F., Stehle, C., Lefevre, R., Chaulagain, U., Champion, N., Barroso, P., Reix, F., Jagourel, P., Larour, J., Delmotte, F., Constancias, C., Suzuki-Vidal, F., & Acef, O. (2014). Characterization of Zn X-Ray Laser at PALS Centre, Its Applications in Dense Plasma Probing and Astrophysics. In X-RAY LASERS 2012 (Vol. 147, pp. 151–159).
Résumé: This report presents the results from experiments at PALS Centre using a Zn X-ray laser with the pulse length of 0.15 ns and the wavelength of 21.2 nm, working in single or double pass regime with the output energy of 0.4 mJ or 4 mJ per pulse, respectively. The current X-ray laser was experimentally examined to obtain its temporal coherence and spectral width using a path-difference interferometer. The double pass regime shows that QSS plasma based source-amplifier is promising for “short” fs soft X-ray pulses. The X-ray laser is commonly used for user's experiments. Its advantages can be shown in applications such as probing of dense plasmas (up to 2.5 x 10(24) cm(-3)) or single shot experiments (4 x 10(14) photons/pulse). The simple technique based on Talbot effect was used to obtain the gradients of electron densities of line plasmas produced under conditions corresponding to XRL's amplifiers operating in TCE and QSS regime. To investigate radiative shock wave in laboratory is challenging in aspects of the optimization of experimental parameters. Due to the high electron density (10(22) cm(-3)) produced in the gas medium propagated by the shock wave, the velocity of the shock wave, and the absorption losses on optical elements, it is necessary to use the energetic single shot probe.
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Meng, L., Calisti, A., Ferri, S., Mosse, C., Talin, B., Benredjem, D., Guilbaud, O., & Klisnick, A. (2014). Spectral Broadening of Ni-Like XUV Laser Lines. In X-RAY LASERS 2012 (Vol. 147, pp. 181–184).
Résumé: We have used the PPP lineshape code to calculate the intrinsic (i.e. before amplification) line profile of the Mo XUV laser over an extended range of plasma densities and temperatures, chosen to cover conditions for collisional excitation pumping in the transient and quasi-steady state regimes. The calculated profiles were then used to simulate the amplified line profile, using a detailed 1D-radiative transfer code, taking into account the effect of saturation. We discuss the possibility to achieve a gain bandwidth that would support pulse amplification below 1 ps.
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Meng, L., Klisnick, A., Kozlova, M., Bohacek, K., Krus, M., Prokupek, J., Urbanski, L., Marconi, M. C., Berrill, M., Rocca, J. J., Guilbaud, O., Tissandier, F., Sebban, S., Zeitoun, P., Calisti, A., Ferri, S., Mosse, C., & Talin, B. (2014). Temporal Coherence and Spectral Linewidth of Neon-Like XUV Lasers Pumped in the Quasi-steady State Regime. In X-RAY LASERS 2012 (Vol. 147, pp. 175–180).
Résumé: We report recent experimental progress in the characterization of the temporal coherence and related spectral linewidth of plasma-based soft X-ray lasers (SXRL). New measurements were carried out with two types of SXRLs pumped in the quasi-steady state (QSS) regime, in a capillary-discharge plasma and in a laser-produced plasma. We describe the main results obtained from both experiments and compare them to dedicated numerical simulations. We discuss the results in the context of the possibility to achieve XUV lasers with pulse duration below 1 picosecond.
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Tchalala, M. R., & Ait Ali, M. (2014). Chemical Synthesis of Silicon sheets from Calcium Silicide. In JOURNAL OF PHYSICS-CONFERENCE SERIES (Vol. 491, 12009).
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Tchalala, M. R., Enriquez, H., Mayne, A. J., Kara, A., Dujardin, G., Ali, M. A., & Oughaddou, H. (2014). Atomic structure of silicene nanoribbons on Ag(110). In JOURNAL OF PHYSICS-CONFERENCE SERIES (Vol. 491, 012002). 3RD INTERNATIONAL MEETING ON SILICENE (IMS-3).
Résumé: The growth of silicene nano-ribbons (NRs) on Ag(110) substrate is re-investigated using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Deposition of one silicon monolayer at 230 degrees C induces the formation of one-dimensional 1.6 nm wide silicene nanoribbons into a well-ordered compact array with a nanometer-scale pitch of just 2 nm. Based on the STM analysis we derived an atomic model of the silicene nanoribbons (NRs) where they are substantially buckled, and quantum confinement of the electrons in the NRs contribute to electronic density of states.
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Tissandier, F., Sebban, S., Kozlova, M., Gautier, J., Zeitoun, P., Klisnick, A., & Maynard, G. (2014). High Density Optical-Field-Ionization Soft X-Ray Lasers. In X-RAY LASERS 2012 (Vol. 147, pp. 243–255).
Résumé: Generating an optical-field-ionization (OFI) collisional soft X-ray laser amplifier in a high density plasma would allow a significant increase of the saturation intensity, laser gain, and reduction of the emitted pulse duration. Due to strong refraction of the pump infrared beam in the plasma, guiding techniques have to be implemented. Using an optically preformed plasma waveguide, we successfully achieved guiding of J-energy pulses in a near-critical density krypton plasma with 50 % total transmission over 5 to 10 mm. X-ray lasing at 32.8 nm has also been demonstrated. This technique is a step towards OFI recombination soft X-ray lasers. This pumping scheme requires the production of a cold and dense plasma. We propose to pump a high density neon VIII plasma by a frequency doubled intense Ti:Sa laser. Guiding of the 405 nm pump pulse has already been achieved at LOA.
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Urbanski, L., Marconi, M. C., Meng, L. M., Berrill, M., Guilbaud, O., Klisnick, A., & Rocca, J. J. (2014). Spectral Linewidth Measurement of a Ne-Like Ar Capillary Discharge Soft X-Ray Laser. In X-RAY LASERS 2012 (Vol. 147, pp. 257–261).
Résumé: We report on the measurement of spectral linewidth of a Ne-like Ar tabletop capillary discharge laser. The linewidth was measured as a function of the gain medium length. Due to inhomogeneous character of the linewidth, saturation rebroadening is expected. However no such behavior was observed while the amplifier length was extended beyond saturation. This situation is compared with a numerical model, identifying that even a small amount of collisional broadening effectively homogenizes the line profile.
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Monographies |
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Physique nucléaire: Des quarks aux applications. (2014). Le Sech C. et Ngô C..
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Chapitres de Livres |
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Le Sech, C. (2014). Quantum Confinement Study of the H2+ Ion and H2 Molecule with Monte Carlo Method. In Electronic Structure of Quantum Confined Atoms and Molecules Sen, K. D., Ed.; Springer: Cham, Switzerland (227).
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Sonnet, P., & Riedel, D. (2014). The Scanning Tunneling Microscopy of Adsorbed Molecules on Semiconductors : Some Theoretical Answers to the Experimental Observations. In Practical Aspects of Computational Chemistry III (Vol. 3, pp. 1–40). Jerzy Leszczynski; Manoj K. Shukla.
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