Peer-reviewed Publications |
Amri S., Corgier R., Sugny D., Rasel E. M., Gaaloul N., & Charron E. (2019). Optimal control of the transport of Bose-Einstein condensates with atom chips. Sci. Rep., 9, 5346.
Résumé: Using Optimal Control Theory (OCT), we design fast ramps for the controlled transport of Bose-Einstein condensates with atom chips’ magnetic traps. These ramps are engineered in the context of precision atom interferometry experiments and support transport over large distances, typically of the order of 1 mm, i.e. about 1,000 times the size of the atomic clouds, yet with durations not exceeding 200 ms. We show that with such transport durations of the order of the trap period, one can recover the ground state of the final trap at the end of the transport. The performance of the OCT procedure is compared to that of a Shortcut-To-Adiabaticity (STA) protocol and the respective advantages/disadvantages of the OCT treatment over the STA one are discussed.
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Atabek, O., & Lefebvre, R. (2019). Zero-width resonances in the context of Fano's configuration interaction formalism. Molecular Physics, 117(15-16), 2010–2013.
Résumé: We examine how to link two approaches for resonance width calculations, in a situation of crossing of two diatomic molecular potentials. One is the semiclassical formalism of Child. The other is Fano's configuration interaction approach leading to the Fermi golden rule. We build a case where the vanishing of the width in the two formalisms can be reduced to the same conditions.
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Chamakhi R., Telmini M., Atabek O., & Charron E. (2019). Anisotropy control in photoelectron spectra: A coherent two-pulse interference strategy. Phys. Rev. A, 100, 033402.
Résumé: Coherence among rotational ion channels during photoionization is exploited to control the anisotropy of the resulting photoelectron angular distributions at specific photoelectron energies. The strategy refers to a robust and single parameter control using two ultrashort light pulses delayed in time. The first pulse prepares a superposition of a few ion rotational states, whereas the second pulse serves as a probe that gives access to a control of the molecular asymmetry parameter β for individual rotational channels. This is achieved by tuning the time delay between the pulses, leading to channel interferences that can be turned from constructive to destructive. The illustrative example is the ionization of the E(1Σg+) state of Li2. Quantum wave-packet evolutions are conducted including both electronic and nuclear degrees of freedom to reach angle-resolved photoelectron spectra. A simple interference model based on coherent phase accumulation during the field-free dynamics between the two pulses is precisely exploited to control the photoelectron angular distributions from almost isotropic to marked anisotropic.
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Chin, A. W., Mangaud, E., Chevet, V., Atabek, O., & Desouter-Lecomte, M. (2019). Visualising the role of non-perturbative environment dynamics in the dissipative generation of coherent electronic motion. Chemical Physics, 525, 110392.
Résumé: Targeted exciton transport is crucial for efficient light-harvesting, but its microscopic description in biological systems is complicated by strong environmental coupling, highly structured vibrational environments and non-Markovian open system dynamics. In this article we employ the non-perturbative hierarchical equations of motion (HEOM) technique to explore how structured environments and tuned electronic properties can lead to the generation of coherent motion across a directed transport network, i.e. one containing an energy gradient. By further exploiting the information contained in the auxiliary HEOM matrices, we also visualize the complete displacement distributions of the main reaction coordinate during the ultrafast relaxation, and show that highly non-Gaussian profiles emerge when the electronic dynamics become quasi-reversible and involve bath-induced delocalized states. These coherent dynamics are spontaneously generated by earlier incoherent relaxation events, and we also demonstrate the correlation between the environmental coordinates and a quantitative volume-based measure of non-Markovianity.
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Devolder, A., Luc-Koenig, E., Atabek, O., Desouter-Lecomte, M., & Dulieu, O. (2019). Laser-assisted self-induced Feshbach resonance for controlling heteronuclear quantum gas mixtures. Phys. Rev. A, 100(5), 052703.
Résumé: We propose a type of Feshbach resonance occurring when two different ultracold atoms in their ground state undergo an s-wave collision in the presence of a laser. The collisional levels of the atom pair are coupled by the laser to a rovibrational molecular level of the same electronic ground state: We name it a laser-assisted self-induced Feshbach resonance. This mechanism, valid for all heteronuclear quantum gas mixtures, is analyzed on the example of ultracold 87Rb and 84Sr atoms for which the resonant laser frequency falls in the subterahertz range. The interspecies scattering length can be controlled with the laser frequency and intensity without atom loss. Moreover, chirping slowly, the frequency allows for the adiabatic formation of ultracold 87Rb84Sr molecules in a manner very similar to a magnetic Feshbach resonance. A stimulated Raman adiabatic passage follows for stabilizing the molecules in their rovibronic ground state.
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Gonon, B., Lasorne, B., Karras, G., Joubert-Doriol, L., Lauvergnat, D., Billard, F., Lavorel, B., Faucher, O., Guerin, S., Hertz, E., & Gatti, F. (2019). A generalized vibronic-coupling Hamiltonian for molecules without symmetry: Application to the photoisomerization of benzopyran. J Chem Phys, 150(12), 124109.
Résumé: We present a model for the lowest two potential energy surfaces (PESs) that describe the photoinduced ring-opening reaction of benzopyran taken as a model compound to study the photochromic ring-opening reaction of indolinobenzospiropyran and its evolution toward its open-chain analog. The PESs are expressed in terms of three effective rectilinear coordinates. One corresponds to the direction between the equilibrium geometry in the electronic ground state, referred to as the Franck-Condon geometry, and the minimum of conical intersection (CI), while the other two span the two-dimensional branching space at the CI. The model correctly reproduces the topography of the PESs. The ab initio calculations are performed with the extended multiconfiguration quasidegenerate perturbation theory at second order method. We demonstrate that accounting for electron dynamic correlation drastically changes the global energy landscape since some zwitterionic states become strongly stabilized. Quantum dynamics calculations using this PES model produce an absorption spectrum that matches the experimental one to a good accuracy.
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Hrodmarsson, H. R., Thissen, R., Dowek, D., Garcia, G. A., Nahon, L., & Govers, T. R. (2019). Isotope Effects in the Predissociation of Excited States of N2 (+) Produced by Photoionization of (14)N2 and (15)N2 at Energies Between 24.2 and 25.6 eV. Front Chem, 7(222).
Résumé: Photoelectron/photoion imaging spectrometry employing dispersed VUV radiation from the SOLEIL synchrotron has been used to study the predissociation of N2 (+) states located up to 1.3 eV above the ion's first dissociation limit. Branching ratios for unimolecular decay into either N2 (+) or N(+) were obtained by measuring coincidences between threshold electrons and mass-selected product ions, using a supersonic beam of either (14)N2 or (15)N2 as photoionization target. The results confirm that predissociation of the C 2 Sigma u + state of (14)N2 (+) is faster than emission to the electronic ground-state by a factor 10 or more for all vibrational levels v' >/= 3, while for (15)N2 (+) the two decay modes have comparable probabilities for the levels v' = 3, 4, and 5. In contrast, no significant isotope effect could be observed for the other states of N2 (+) identified in the photoelectron spectrum. For both (14)N2 (+) and (15)N2 (+) isotopologues all vibrational levels of these other states decay to an extent of at least 95% by predissociation.
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Latka, T., Shirvanyan, V., Ossiander, M., Razskazovskaya, O., Guggenmos, A., Jobst, M., Fieß, M., Holzner, S., Sommer, A., Schultze, M., Jakubeit, C., Riemensberger, J., Bernhardt, B., Helml, W., Gatti, F., Lasorne, B., Lauvergnat, D., Decleva, P., Halász, G., Vibók, A., & Kienberger, R. (2019). Femtosecond wave-packet revivals in ozone. Phys. Rev. A, 99(6), 063405.
Résumé: Photodissociation of ozone following absorption of biologically harmful solar ultraviolet radiation is the key mechanism for the life protecting properties of the atmospheric ozone layer. Even though ozone photolysis is described successfully by post-Hartree-Fock theory, it has evaded direct experimental access so far, due to the unavailability of intense ultrashort deep ultraviolet radiation sources. The rapidity of ozone photolysis with predicted values of a few tens of femtoseconds renders both ultrashort pump and probe pulses indispensable to capture this manifestation of ultrafast chemistry. Here, we present the observation of femtosecond time-scale electronic and nuclear dynamics of ozone triggered by ∼10-fs, ∼2-µJ deep ultraviolet pulses and, in contrast to conventional attochemistry experiments, probed by extreme ultraviolet isolated pulses. An electronic wave packet is first created. We follow the splitting of the excited B-state related nuclear wave packet into a path leading to molecular fragmentation and an oscillating path, revolving around the Franck-Condon point with 22-fs wave-packet revival time. Full quantum-mechanical ab initio multiconfigurational time-dependent Hartree simulations support this interpretation.
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Mangaud E, Lasorne B, Atabek, O., & Desouter-Lecomte M. (2019). Statistical distributions of the tuning and coupling collective modes at a conical intersection using the hierarchical equations of motion. J Chem Phys, 151(24), 244102.
Résumé: We investigate the possibility of extracting the probability distribution of the effective environmental tuning and coupling modes during the nonadiabatic relaxation through a conical intersection. Dynamics are dealt with an open quantum system master equation by partitioning a multistate electronic subsystem out of all the nuclear vibrators. This is an alternative to the more usual partition retaining the tuning and coupling modes of a conical intersection in the active subsystem coupled to a residual bath. The minimal partition of the electronic system generally leads to highly structured spectral densities for both vibrational baths and requires a strongly nonperturbative non-Markovian master equation, treated here by the hierarchical equations of motion (HEOMs). We extend-for a two-bath situation-the procedure proposed by Shi et al. [J. Chem. Phys. 140, 134106 (2014)], whereby the information contained in the auxiliary HEOM matrices is exploited in order to derive the nuclear dissipative wave packet, i.e., the statistical distribution of the displacement of the two tuning and coupling collective coordinates in each electronic state and the coherence. This allows us to visualize the distribution, all along the nonadiabatic decay. We explore a large parameter space for a symmetrical conical intersection model and a symmetrical initial Franck-Condon preparation. Some parameters could be controlled by external fields, while others are molecule dependent and could be designed by molecular engineering. We illustrate the relation between the strongly coupled electronic and bath dynamics together with a geometric measure of non-Markovianity.
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Ndengué, S. A., Scribano, Y., Benoit, D. M., Gatti, F., & Dawes, R. (2019). Intermolecular rovibrational bound states of H2O H2 dimer from a MultiConfiguration Time Dependent Hartree approach. Chemical Physics Letters, 715, 347–353.
Résumé: We compute the rovibrational eigenstates of the H2O-H2 Van der Waals complex using the accurate rigid-rotor potential energy surface of Valiron et al. (2008) with the MultiConfiguration Time Dependent Hartree (MCTDH) method. The rovibrational bound states calculations are done with the Block Improved Relaxation procedure of MCTDH and the subsequent assignment of the states is achieved by inspection of the wavefunctions’ properties. The results of this work are found to be in close agreement with previous time independent calculations reported for this complex and therefore supports the use of the MCTDH approach for the rovibrational spectroscopic study of such weakly bound complexes.
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Trimeche A., Battelier B., Becker D., Bertoldi A., Bouyer P., Braxmaier C., Charron E., Corgier R., Cornelius M., Douch K., Gaaloul N., Herrmann S., Müller J., Rasel E., Schubert C., Wu H., & Pereira dos Santos F. (2019). Concept study and preliminary design of a cold atom interferometer for space gravity gradiometry. Clas. Quant. Grav., 36, 215004.
Résumé: We study a space-based gravity gradiometer based on cold atom interferometry and its potential for the Earth's gravitational field mapping. The instrument architecture has been proposed in Carraz et al (2014 Microgravity Sci. Technol. 26 139) and enables high-sensitivity measurements of gravity gradients by using atom interferometers in a differential accelerometer configuration. We present the design of the instrument including its subsystems and analyze the mission scenario, for which we derive the expected instrument performances, the requirements on the sensor and its key subsystems, and the expected impact on the recovery of the Earth gravity field.
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Ueda, K., Sokell, E., Schippers, S., Aumayr, F., Sadeghpour, H., Burgdörfer, J., Lemell, C., Tong, X. - M., Pfeifer, T., Calegari, F., Palacios, A., Martin, F., Corkum, P., Sansone, G., Gryzlova, E. V., Grum-Grzhimailo, A. N., Piancastelli, M. N., Weber, P. M., Steinle, T., Amini, K., Biegert, J., Berrah, N., Kukk, E., Santra, R., Müller, A., Dowek, D., Lucchese, R. R., McCurdy, C. W., Bolognesi, P., Avaldi, L., Jahnke, T., Schöffler, M. S., Dörner, R., Mairesse, Y., Nahon, L., Smirnova, O., Schlathölter, T., Campbell, E. E. B., Rost, J. - M., Meyer, M., & Tanaka, K. A. (2019). Roadmap on photonic, electronic and atomic collision physics: I. Light–matter interaction. J. Phys. B: At. Mol. Opt. Phys., 52, 171001.
Résumé: We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light–matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field.
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Yuen, C. H., Lapierre, D., Gatti, F., Kokoouline, V., & Tyuterev, V. G. (2019). The Role of Ozone Vibrational Resonances in the Isotope Exchange Reaction (16)O(16)O + (18)O --> (18)O(16)O + (16)O: The Time-Dependent Picture. J Phys Chem A, 123(36), 7733–7743.
Résumé: We consider the time-dependent dynamics of the isotope exchange reaction in collisions between an oxygen molecule and an oxygen atom: (16)O(16)O + (18)O --> (16)O(18)O + (16)O. A theoretical approach using the multiconfiguration time-dependent Hartree method was employed to model the time evolution of the reaction. Two potential surfaces available in the literature were used in the calculations, and the results obtained with the two surfaces are compared with each other as well as with results of a previous theoretical time-independent approach. A good agreement for the reaction probabilities with the previous theoretical results is found. Comparing the results obtained using two potential energy surfaces allows us to understand the role of the reef/shoulder-like feature in the minimum energy path of the reaction in the isotope exchange process. Also, it was found that the distribution of final products of the reaction is highly anisotropic, which agrees with experimental observations and, at the same time, suggests that the family of approximated statistical approaches, assuming a randomized distribution over final exit channels, is not applicable to this case.
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Zhang, Z., Zhang Z, Gatti, F., Gatti F, Zhang, D. H., & Zhang DH. (2019). Full dimensional quantum mechanical calculations of the reaction probability of the H + NH3 collision based on a mixed Jacobi and Radau description. J Chem Phys, 150(20), 204301.
Résumé: The collision between hydrogen and ammonia is a benchmark system to study chemical elementary reactions with five atoms. In this work, we present a description of the system based on mixed Jacobi and Radau coordinates combined with the time-dependent wave packet method to study the H + NH3 reaction. The Radau coordinates are used to describe the reactive moiety NH2. A salient feature of this approach is that the present coordinates have a great advantage that a very small number of basis set functions can be used to describe the NH2 group. Potential-optimized discrete variable representation basis is applied for the vibrational coordinates of the reagent NH3. The reaction probabilities for several initial vibrational states are presented in this paper. The role of the different vibrational excitations on the reactivity is thoroughly described.
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Actes de Conférences |
Kennedy, E. T., Mosnier, J. P., Van Kampen, P., Bizau, J. - M., Cubaynes, D., Guilbaud, S., Carniato, S., Puglisi, A., & Sisourat, N. (2019). Vibrational effects in the photo-ion yield spectrum of the SiH<sub>2</sub><sup>+</sup>molecular ion following 2p inner-shell excitation. In Journal of Physics: Conference Series (Vol. 1289, 012003).
Résumé: We report on complementary theoretical and laboratory investigations of the 2p ion yield cross sections for the molecular-ion series SiHn+ (n = 1, 2, 3), in the 95-108 eV photon energy range, below the L-shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatised synchrotron radiation in a merged-beam configuration. The experimental spectra are compared with total photoabsorption cross-sectional profiles calculated using an ab initio configuration interaction method inclusive of spin-orbit coupling and the vibrational dynamics. The experimental results show vibrationally resolved resonances for SiH2+ in the 98-102 eV range. The calculations indicate twenty four core-excited states below the energy of 102 eV, of which only four contribute significantly to the observed spectrum. These states correspond to the excitation of an atomic-like 2p electron to the SiH2+ (5a1) valence orbital.
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