Peer-reviewed Publications |
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Atabek, O. (2012). Ultrafast intense laser induced molecular dissociation: Imaging and control. Balkan Physics Letters, 20, 37.
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Billaud, P., Geleoc, M., Picard, Y. J., Veyrinas, K., Hergott, J. F., Poullain, S. M., Breger, P., Ruchon, T., Roulliay, M., Delmotte, F., Lepetit, F., Huetz, A., Carre, B., & Dowek, D. (2012). Molecular frame photoemission in dissociative ionization of H-2 and D-2 induced by high harmonic generation femtosecond XUV pulses. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 45(19), 194013.
Résumé: We report the first results of molecular frame photoelectron emission for dissociative photoionization (DPI) of H-2 and D-2 molecules induced by a spectrally filtered single high harmonic of a few femtosecond duration, using coincident electron-ion velocity vector correlation techniques. For the studied photon energies around 32 eV, where the resonant excitation of the Q(1) and Q(2) doubly excited states occurs, autoionization and nuclear dynamics are coupled on a few femtosecond timescale, giving rise to quantum interferences. Molecular frame photoelectron angular distributions (MFPADs), traced as a function of the kinetic energy release of the atomic fragments, provide the most sensitive observables for such complex dynamics. These results compare well with recent spectrally resolved experiments using synchrotron radiation which are also reported. As a novel XUV light source running at multi-kHz repetition rate and synchronized with laser pulses, high-order harmonic generation (HHG) opens new possibilities for extending these investigations to time-resolved studies at the femtosecond scale.
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Blancard, C., Cosse, P., Faussurier, G., Bizau, J. - M., Cubaynes, D., El Hassan, N., Guilbaud, S., Al Shorman, M. M., Robert, E., Liu, X. - J., Nicolas, C., & Miron, C. (2012). L-shell photoionization of Ar+ to Ar3+ ions. PHYSICAL REVIEW A, 85(4), 043408.
Résumé: Absolute photoionization cross sections of Ar+, Ar2+, and Ar3+ ions have been measured in the 250-280 eV photon energy range. These results are compared to theoretical cross sections extracted from two new calculations we performed. They reproduce well the general behavior of the experimental spectra and the magnitude of the direct photoionization cross sections. However, the oscillator strength of the resonant structure in the spectra, dominated by 2p -> 3d transitions, is overestimated up to 80% by our calculations.
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Borges, C. V. S., Khoury, A. Z., Walborn, S., Ribeiro, P. H. S., Milman, P., & Keller, A. (2012). Bell inequalities with continuous angular variables. Phys. Rev. A., 86(5), 052107.
Résumé: We consider bipartite quantum systems characterized by a continuous angular variable., representing, for instance, the position of a particle on a circle or in a periodic lattice. For this type of system, we show how to violate inequalities similar to Clauser-Horne-Shimony-Holt (CHSH) ones, originally derived for bipartite spin-1/2-like systems. Such inequalities involve correlated measurement of continuous angular functions and are equivalent to the continuous superposition of CHSH inequalities acting on bidimensional subspaces of the infinite dimensional Hilbert space. As an example, we discuss in detail one application of our results, and we derive inequalities based on orientation correlation measurements. The introduced Bell-type inequalities open the perspective of new and simpler experiments to test the assumptions of locality, realism, or freedom of choice in a variety of quantum systems described by continuous variables. We discuss in detail a possible implementation using the orbital angular momentum of photons.
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Lebech, M., Houver, J. C., Raseev, G., dos Santos, A. S., Dowek, D., & Lucchese, R. R. (2012). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions. JOURNAL OF CHEMICAL PHYSICS, 136(9), 094303.
Résumé: Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 eV, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 (2)Delta state with an ionization potential of 25.3 eV and (2)Sigma(+) states with ionization potentials near 32.5 eV. A comparison of the experimental and theoretical RFPADs permits us to estimate predissociative lifetimes of 0.25-1 ps for some of the ion states. Consideration of the MFPADs of a series of (2)Pi ion states indicates the importance of inter-channel coupling at low photoelectron kinetic energy and the limitations of a single-channel analysis based on the corresponding Dyson orbitals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3681920]
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Lefebvre, R., Jaouadi, A., & Atabek, O. (2012). Clusters of exceptional points for a laser control of selective vibrational transfer. Chemical Physics, 399, 111.
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Li, C., Casagrande, E. M. S., Lahmam-Bennani, A., & Naja, A. (2012). Identification of first order and non-first order contributions in the (e,3-1e) and (e,3e) double ionization of molecular nitrogen. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 45(13), 135201.
Résumé: Double ionization of nitrogen molecules is investigated in coplanar asymmetric (e,3-1e) and (e,3e) experiments. The measurements are performed at intermediate incident energy (similar to 600 eV) with one fast scattered electron and two slower ejected electrons sharing equally the excess energy. The data are compared with the predictions of a simple kinematical model recently reported by Lahmam-Bennani et al (2010 J. Phys. B: At. Mol. Opt. Phys. 43 105201) which describes the 'two-step 2' (TS2) mechanism as two successive (e,2e) single ionization interactions. The model is extended to include binary as well as recoil scattering during the two successive single ionization events. It is shown to qualitatively predict the correct angular positions for most of the observed structures. Moreover, the (e,3e) data are compared with the predictions of a first Born model which fails to reproduce the experimental angular distributions. These results demonstrate that the molecular double ionization process is largely dominated by the TS2 mechanism, as was the case in our previous works on atomic targets.
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Meng, L., Bourgaux, A. - C., Bastiani-Ceccotti, S., Guilbaud, O., Pittman, M., Kazamias, S., Cassou, K., Daboussi, S., Ros, D., & Klisnick, A. (2012). Temporal characterization of a picosecond extreme ultraviolet laser pumped in grazing incidence. APPLIED PHYSICS LETTERS, 101(14), 141125.
Résumé: We report an experimental study of the temporal duration of a transient pumping extreme ultraviolet (XUV) laser emitted at 18.9 nm, using an ultrafast x-ray streak camera. We have investigated the shot-to-shot reproducibility of the pulse duration, as well as its behaviour as a function of several pumping parameters. Our results show that the pulse duration increases slowly with the pump pulse duration, in agreement with previous observations performed in a different geometry. The angle of the pump laser relative to the target surface also affects the XUV laser duration in a measurable way. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757878]
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Peters, M., Nguyen-Dang, T. T., Charron, E., Keller, A., & Atabek, O. (2012). Laser-induced electron diffraction: A tool for molecular orbital imaging. PHYSICAL REVIEW A, 85(5), 053417.
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Richardson, V., Li, W. B., Kelly, T. J., Costello, J. T., Nikolopoulos, L. A. A., Duesterer, S., Cubaynes, D., & Meyer, M. (2012). Dichroism in the above-threshold two-colour photoionization of singly charged neon. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 45(8), 085601.
Résumé: In this work we report on the ionization of a gaseous neon target by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. Applying energy-resolved photoelectron spectroscopy, the dependence of the electrons ejected from singly charged neon (Ne+) on the relative polarization of the XUV and optical laser fields was investigated. The electron spectra exhibit a strong dependence on the degree of the relative orientation of the linear polarization vectors. A quantitative analysis was undertaken using multichannel time-dependent perturbation theory in order to reproduce the magnitude of the ejected low kinetic energy electrons as a function of the relative polarization directions and explicitly taking into account the influence of the residual Ne2+ cores (D-1, P-3). It is concluded that the variation of the photoelectron spectrum with the deviation of XUV and optical field directions is mainly related to the different responses of the magnetic substates of the ejected electrons in their interaction with the laser field.
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Urbanski, L., Marconi, M. C., Meng, L. M., Berrill, M., Guilbaud, O., Klisnick, A., & Rocca, J. J. (2012). Spectral linewidth of a Ne-like Ar capillary discharge soft-x-ray laser and its dependence on amplification beyond gain saturation. PHYSICAL REVIEW A, 85(3), 033837.
Résumé: We report the measurement of the linewidth and temporal coherence of a lambda=46.9 nm neon-like argon capillary discharge soft-x-ray laser and its variation with plasma column length. A wave-front-division interferometer was used to resolve the 3p S-1(0)-3s P-1(1) laser line, resulting in measured relative linewidths of Delta lambda/lambda = (3-4) x 10(-5). The measurements do not observe saturation rebroadening when this clearly dominantly Doppler-broadened inhomogeneous line is amplified beyond the intensity corresponding to gain saturation. Model simulations indicate this is the result of a comparatively small collisional broadening that sufficiently homogenizes the line profile to practically eliminate inhomogeneous saturation rebroadening. Collisional redistribution is computed to play only a very minor role in homogenizing the line profile.
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Actes de Conférences |
Billaud, P., Picard, Y. J., Geleoc, M., Hergott, J. - F., Carre, B., Breger, P., Ruchon, T., Veyrinas, K., Roulliay, M., Delmotte, F., Boettcher, M., Huetz, A., & Dowek, D. (2012). Ultrafast Electronic And Nuclear Dynamics In Dissociative Photoionization Of Molecular Hydrogen and Deuterium. In XXVII INTERNATIONAL CONFERENCE ON PHOTONIC (Vol. 388).
Résumé: Single-photon dissociative photoionization of H-2/D-2 in the Q(1), Q(2) doubly excited states resonance regions, where ultrafast electronic and nuclear dynamics are coupled, is studied using the vector-correlation method with single selected femtosecond high-order harmonic and synchrotron radiation in the VUV. Results are compared at the level of electron-ion kinetic energy correlation diagrams, asymmetry parameters, and the molecular frame photoelectron angular distributions.
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Bizau, J. M., Cubaynes, D., Al Shorman, M. M., Guilbaud, S., Blancard, C., Lemaire, J., Thissen, R., Giuliani, A., Nicolas, C., & Milosavljevic, A. R. (2012). Photoionization of atomic and molecular positively charged ions. In 26TH SUMMER SCHOOL AND INTERNATIONAL SYMPOSIUM ON THE PHYSICS OF IONIZED GASES (SPIG 2012) (Vol. 399).
Résumé: We compare advantages and drawbacks of the two techniques mainly used for the experimental study of gas phase photoionization processes on ionic targets in combination with synchrotron radiation, the merged beam and ion trap. The comparison will be illustrated by recent results obtained on atomic and small molecular positively charged ions using both techniques at SOLEIL, the French synchrotron radiation facility.
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Gharaibeh, M. F., Bizau, J. - M., Cubaynes, D., Guilbaud, S., El Hassan, N., Al Shorman, M. M., Blancard, C., & McLaughlin, B. M. (2012). K-Shell Photoionization of Singly Ionized Atomic Nitrogen. In XXVII ICPEAC Journal of Physics: Conference Series (Vol. 388).
Résumé: K-shell photoionization cross-section measurements for singly ionized atomic nitrogen made at the SOLEIL Light Source for the first time are compared with MCDF and R-matrix calculations.
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Klisnick, A. (2012). Plasma-based XUV lasers. In SHORT-WAVELENGTH IMAGING AND SPECTROSCOPY SOURCES (SPIE-INT SOC OPTICAL ENGINEERING ed., Vol. 8678, 867803). Proceedings of SPIE, 8678.
Résumé: This lecture is an introduction to the generation of plasma-based XUV lasers and their use as a source for scientific applications. We first discuss the main conditions required to create population inversions and amplify XUV radiation. We give an overview of the main properties of the different types of XUV lasers beams that are currently operational worldwide, while comparing them to other ultrashort, high-brightness sources existing in the same spectral range. We discuss recent demonstrations of applications of plasma-based XUV lasers to high-resolution imaging and interaction with matter at high intensity. Finally we conclude with current prospects for extending these sources to shorter wavelength and higher output intensity.
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Richardson, V., Costello, J. T., Nikolopoulos, L. A. A., Duesterer, S., Cubaynes, D., Meyer, M., & Li, W. B. (2012). Above-threshold two-colour ionization signal of singly charged neon. In XXVII ICPEAC Journal of Physics: Conference Series (Vol. 388).
Résumé: In this work we report the ionization of a gaseous neon target by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. The photoelectron spectrum dependence of the electrons ejected from singly-charged neon (Ne+) on the relative polarisation of the XUV and optical laser fields was investigated both experimentally and theoretically.
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