Peer-reviewed Publications |
Bossion, D., Ndengue, S., Meyer, H. - D., Gatti, F., & Scribano, Y. (2020). Theoretical investigation of the H + HD --> D + H2 chemical reaction for astrophysical applications: A state-to-state quasi-classical study. J Chem Phys, 153(8), 081102.
Résumé: We report a large set of state-to-state rate constants for the H + HD reactive collision, using Quasi-Classical Trajectory (QCT) simulations on the accurate H3 global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. High relative collision energies (up to approximately 56 000 K) and high rovibrational levels of HD (up to approximately 50 000 K), relevant to various non thermal equilibrium astrophysical media, are considered. We have validated the accuracy of our QCT calculations with a new efficient adaptation of the Multi Configuration Time Dependent Hartree (MCTDH) method to compute the reaction probability of a specific reactive channel. Our study has revealed that the high temperature regime favors the production of H2 in its highly rovibrationnally excited states, which can de-excite radiatively (cooling the gas) or collisionally (heating the gas). Those new state-to-state QCT reaction rate constants represent a significant improvement in our understanding of the possible mechanisms leading to the destruction of HD by its collision with a H atom.
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Carniato, S., Bizau, J. - M., Cubaynes, D., Kennedy, E. T., Guilbaud, S., Sokell, E., McLaughlin, B., & Mosnier, J. - P. (2020). Vibrationally and Spin-Orbit-Resolved Inner-Shell X-ray Absorption Spectroscopy of the NH+ Molecular Ion: Measurements and ab Initio Calculations. Atoms, 8(4), 67.
Résumé: his article presents N2+ fragment yields following nitrogen K-shell photo-absorption in the NH+ molecular ion measured at the SOLEIL synchrotron radiation facility in the photon energy region 390–450 eV. The combination of the high sensitivity of the merged-beam, multi-analysis ion apparatus (MAIA) with the high spectral resolution of the PLEIADES beamline helped to resolve experimentally vibrational structures of highly excited [N1s−1H]*+ electronic states with closed or open-shell configurations. The assignment of the observed spectral features was achieved with the help of density functional theory (DFT) and post-Hartree Fock Multiconfiguration Self-Consistent-Field/Configuration Interaction (MCSCF/CI) ab-initio theoretical calculations of the N1s core-to-valence and core-to-Rydberg excitations, including vibrational dynamics. New resonances were identified compared to previous work, owing to detailed molecular modeling of the vibrational, spin-orbit coupling and metastable state effects on the spectra. The latter are evidenced by spectral contributions from the 4Σ− electronic state which lies 0.07 eV above the NH+2Π ground state.
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Carniato, S., Selles, P., Ferté, A., Berrah, N., Wuosmaa, A. H., Nakano, M., Hikosaka, Y., Ito, K., Žitnik, M., Bučar, K., Soejima, K., Jänkälä, K., Cubaynes, D., Bizau, J. - M., Andric, L., Khalal, M. A., Palaudoux, J., Lablanquie, P., & Penent, F. (2020). Single photon simultaneous K-shell ionization/excitation in C6H6: experiment and theory. J. Phys. B: At. Mol. Opt. Phys., 53(24), 244010.
Résumé: Single photon simultaneous core ionization/core excitation (K−2V) of the Benzene molecule has been observed experimentally, using synchrotron radiation, by electron coincidence spectroscopy with a magnetic bottle time-of-flight electron spectrometer and reveals a rich spectrum. DFT and Post–Hartree–Fock calculations provide detailed assignments of K−2V states. The specific Auger decay of these states has also been determined experimentally with a new technique to improve the energy resolution.
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Chin, A. W., Le Dé, B., Mangaud, E., Atabek, O., & Desouter-Lecomte, M. (2020). Role of the multiple-excitation manifold in a driven quantum simulator of an antenna complex. Phys. Rev. A, 102(2), 023708.
Résumé: Biomolecular light-harvesting antennas operate as nanoscale devices in a regime where the coherent interactions of individual light, matter, and vibrational quanta are nonperturbatively strong. The complex behavior arising from this could, if fully understood, be exploited for myriad energy applications. However, nonperturbative dynamics are computationally challenging to simulate, and experiments on biomaterials explore very limited regions of the nonperturbative parameter space. So-called quantum simulators of light-harvesting models could provide a solution to this problem, and here we employ the hierarchical equations-of-motion technique to investigate the recent superconducting experiments of Potočnik et al. [A. Potočnik et al., Nat. Commun. 9, 904 (2018)] used to explore excitonic energy capture. By explicitly including the role of optical driving fields, nonperturbative dephasing noise, and the full multiexcitation Hilbert space of a three-qubit quantum circuit, we predict the measurable impact of these factors on transfer efficiency. By analysis of the eigenspectrum of the network, we uncover a structure of energy levels that allows the network to exploit optical “dark” states and excited-state absorption for energy transfer. We also confirm that time-resolvable coherent oscillations could be experimentally observed, even under the strong, nonadditive action of the driving and optical fields.
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Corgier, R., Loriani, S., Ahlers, H., Posso-Trujillo, K., Schubert, C., Rasel, E. M., Charron, E., & Gaaloul, N. (2020). Interacting quantum mixtures for precision atom interferometry. New J. Phys., 22(12), 123008.
Résumé: We present a source engineering concept for a binary quantum mixture suitable as input for differential, precision atom interferometry with drift times of several seconds. To solve the non-linear dynamics of the mixture, we develop a set of scaling approach equations and verify their validity contrasting it to the one of a system of coupled Gross–Pitaevskii equations. This scaling approach is a generalization of the standard approach commonly used for single species. Its validity range is discussed with respect to intra- and inter-species interaction regimes. We propose a multi-stage, non-linear atomic lens sequence to simultaneously create dual ensembles with ultra-slow kinetic expansion energies, below 15 pK. Our scheme has the advantage of mitigating wave front aberrations, a leading systematic effect in precision atom interferometry.
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Jänkälä, K., Lablanquie, P., Andric, L., Khalal, M. A., Palaudoux, J., Penent, F., Bizau, J. - M., Cubaynes, D., Guilbaud, S., Ito, K., Bučar, K., Žitnik, M., Huttula, M., Kaneyasu, T., & Hikosaka, Y. (2020). Core-hole spectator Auger decay. Phys. Rev. A, 101(2), 023413.
Résumé: For an atomic state with two electrons missing from different core orbitals one may assume that the deeper hole decays first. However, it is quite probable that the double core-hole state will decay by emission of a slow Auger electron where the deeper core hole remains a spectator, especially if the outer core hole can be filled by Coster-Kronig transition, while the deeper cannot. We study here the competition of both Auger decay channels in a model system, the 1s2s2p6(3s/3p) states of Ne+ ions. As the phenomenon can take place in any decay chain involving multiple core-excited states it can be critical to understand the ion yields, the electron and x-ray emission spectra, and the molecular fragmentation.
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Joseph, J., Holzmeier, F., Bresteau, D., Spezzani, C., Ruchon, T., Hergott, J. - F., Tcherbakoff, O., D’Oliveira, P., Houver, J. - C., & Dowek, D. (2020). Angle-resolved studies of XUV–IR two-photon ionization in the RABBITT scheme. J. Phys. B: At. Mol. Opt. Phys., 53, 184007.
Résumé: Reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) is an established technique for studying time-delay in photoionization of atoms and molecules. It has been recently extended to angle-resolved studies, accessing diverse fingerprint observables of the attosecond photoemission dynamics within the bound-continuum and continuum–continuum transitions. In this work, we address the general form of the ISB(θ,τ) two-photon photoelectron angular distributions (PADs) associated to the RABBITT sideband signal, as a function of the emission angle θ, and the delay τ between the XUV attosecond pulse train and the infrared (IR) dressing field at play in the RABBITT scheme. Relying on the expansion in Legendre polynomials, the PAD is synthesized in terms of a reduced set of coefficients which fully describe both its static (τ-independent) and dynamic (τ-dependent) components and enables us to retrieve any observable characterizing the PAD. This unified framework streamlines the comparison between different experimental or theoretical data sets and emphasizes how some observables depend on the experimental conditions. Along with the modelled analysis, we report new results of angle-resolved RABBITT direct ionization of the np valence orbital of Ar(3p6) and Ne(2p6), employing electron-ion coincidence momentum spectroscopy at the new Attolab facility. In this case, the nine coefficients synthesizing the PAD are further linked to the magnitude and phase of the transition dipole matrix elements, providing a fundamental test of theoretical predictions. Similarities and differences are found between Ar and Ne in the explored low energy region, up to 20 eV above the ionization threshold, where the electron dynamics is most sensitive to electronic correlation. Further interpretation of these results would benefit from a comparison with advanced many-body theoretical simulations.
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Lefebvre, R., & Atabek, O. (2020). Progress toward full optical control of ultracold-molecule formation: Role of scattering Feshbach resonances. Phys. Rev. A, 101(6), 063406.
Résumé: Feshbach resonances play a major role in translationally cold-molecule preparation. In this context, their laser control is of crucial importance. This work is devoted to the depiction of some basic mechanisms of such a control using intense, short laser pulses and referring to nonlinear multiphoton processes. Our goal is to adiabatically transport a Feshbach resonance onto a zero-width resonance, the characteristics of which have already been discussed in the literature. Three processes are then addressed: (i) during the rise of the pulse and its plateau, the preparation of a so-called laser bound molecule (LBM) still stable, but structurally different from the standard chemically bound molecule; (ii) during the pulse switching off, an adiabatic transport of this LBM on a very few excited vibrational levels, and (iii) concomitantly, a filtration strategy to photodissociate all these levels except one, giving thus rise to but a single field-free excited vibrational state. With or without an eventual stimulated Raman adiabatic passage technique to bring all the population to the ground rovibrational state, this opens an alternate for a full optical control of ultracold-molecule formation. The illustrative example, offering the potentiality to be transposed to other diatomics, is H_2^+.
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Pandey, A. K., Papagiannouli, I., Sanson, F., Baynard, E., Demailly, J., Kazamias, S., Pittman, M., Neveu, O., Lucas, B., Le Marec, A., Klisnick, A., Calisti, A., Larroche, O., Ros, D., & Guilbaud, O. (2020). Towards subpicosecond pulses from solid target plasma based seeded soft X-ray laser. Opt Express, 28(20), 28924.
Résumé: We investigate the coherence of plasma-based soft X-ray laser (XRL) for different conditions that can alter the electron density in the gain region. We first measure the source temporal coherence in amplified spontaneous emission (ASE) mode. We develop a data analysis procedure to extract both its spectral width and pulse duration. These findings are in agreement with the spectral line shape simulations and seeded operation experimental results. Utilizing the deduced spectral width and pulse duration in a one-dimensional Bloch-Maxwell code, we reproduce the experimental temporal coherence properties of the seeded-XRL. Finally, we demonstrate efficient lasing in ASE and seeded mode at an electron density two times higher than the routine conditions. In this regime, using Bloch-Maxwell modeling, we predict the pulse duration of the seeded XRL to be approximately 500fs.
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Penent, F., Cubaynes, D., Lablanquie, P., Palaudoux, J., Guilbaud, S., Moustier, O., Guigand, J., & Bizau, J. - M. (2020). Modification of a Cylindrical Mirror Analyzer for High Efficiency Photoelectron Spectroscopy on Ion Beams. Atoms, 8(4), 63.
Résumé: An existing cylindrical mirror analyzer (CMA) that was initially equipped with eight channeltrons detectors has been modified to install large micro-channel plate detectors to perform parallel detection of electrons on an energy range corresponding to ~12% of the mean pass energy. This analyzer is dedicated to photoelectron spectroscopy of ions ionized by synchrotron radiation. The overall detection efficiency is increased by a factor of ~20 compared to the original analyzer. A proof of principle of the efficiency of the analyzer has been done for Xe5+ and Si+ ions and will allow photoelectron spectroscopy on many other ionic species.
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Zhang, Z., Zhang Z, Gatti, F., Gatti F, Zhang, D. H., & Zhang DH. (2020). Full-dimensional quantum mechanical calculations of the reaction probability of the H + CH4 reaction based on a mixed Jacobi and Radau description. J Chem Phys, 152(20), 201101.
Résumé: A full-dimensional time-dependent wave packet study using mixed polyspherical Jacobi and Radau coordinates for the title reaction has been reported. The non-reactive moiety CH3 has been described using three Radau vectors, whereas two Jacobi vectors have been used for the bond breaking/formation process. A potential-optimized discrete variable representation basis has been employed to describe the vibrational coordinates of the reagent CH4. About one hundred billion basis functions have been necessary to achieve converged results. The reaction probabilities for some initial vibrational states are given. A comparison between the present approach and other methods, including reduced and full-dimensional ones, is also presented.
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Actes de Conférences |
Palaudoux, J., Penent, F., Khalal, M., Jänkälä, K., Keskinen, J., Huttula, M., Bizau, J. - M., Cubaynes, D., Guilbaud, S., Zitnik, M., Bucar, K., Ito, K., Andric, L., & Lablanquie, P. (2020). Auger decay of Rubidum atom after 3d-shell ionization. In Journal of Physics: Conference Series (Vol. 1412, 152037).
Résumé: We present here the different Auger decay paths following 3d inner-shell ionization of Rubidium atom and we observe the peculiar behaviour and correlation effects due to the outer, unpaired 5s electron. This electron can be submitted to shake-up during 3d ionization. Also shake-up and shake-down of the outer electron are observed in the Auger decay. Cascade double Auger decay is the dominant process leading to Rb3+ ion.
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