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Wang P, He L, Deng Y, Sun S, Lan P, Lu P. Unveiling Nonsecular Collisional Dissipation of Molecular Alignment. PHYSICAL REVIEW LETTERS 2024; 133:033202. [PMID: 39094146 DOI: 10.1103/physrevlett.133.033202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/17/2024] [Accepted: 06/18/2024] [Indexed: 08/04/2024]
Abstract
We conducted a joint theoretical and experimental study to investigate the collisional dissipation of molecular alignment. By comparing experimental measurements to the quantum simulations, the nonsecular effect in the collision dissipation of molecular alignment was unveiled from the gas-density-dependent decay rates of the molecular alignment revival signals. Different from the conventional perspective that the nonsecular collisional effect rapidly fades within the initial few picoseconds following laser excitation, our simulations of the time-dependent decoherence process demonstrated that this effect can last for tens of picoseconds in the low-pressure regime. This extended timescale allows for the distinct identification of the nonsecular effect from molecular alignment signals. Our findings present the pioneering evidence that nonsecular molecular collisional dissipation can endure over an extended temporal span, challenging established concepts and strengthening our understanding of molecular dynamics within dissipative environments.
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Bournazel M, Ma J, Billard F, Hertz E, Wu J, Boulet C, Faucher O, Hartmann JM. Quantum modeling, beyond secularity, of the collisional dissipation of molecular alignment using the energy-corrected sudden approximation. J Chem Phys 2023; 158:2887565. [PMID: 37125716 DOI: 10.1063/5.0150002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 04/12/2023] [Indexed: 05/02/2023] Open
Abstract
We propose a Markovian quantum model for the time dependence of the pressure-induced decoherence of rotational wave packets of gas-phase molecules beyond the secular approximation. It is based on a collisional relaxation matrix constructed using the energy-corrected sudden approximation, which improves the previously proposed infinite order sudden one by taking the molecule rotation during collisions into account. The model is tested by comparisons with time-domain measurements of the pressure-induced decays of molecular-axis alignment features (revivals and echoes) for HCl and CO2 gases, pure and diluted in He. For the Markovian systems HCl-He and CO2-He, the comparisons between computed and measured data demonstrate the robustness of our approach, even when the secular approximation largely breaks down. In contrast, significant differences are obtained in the cases of pure HCl and CO2, for which the model underestimates the decay rate of the alignment at short times. This result is attributed to the non-Markovianity of HCl-HCl and CO2-CO2 interactions and the important contribution of those collisions that are ongoing at the time when the system is excited by the aligning laser pulse.
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Affiliation(s)
- M Bournazel
- Laboratoire Interdisciplinaire CARNOT de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon, France
| | - J Ma
- Laboratoire Interdisciplinaire CARNOT de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon, France
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - F Billard
- Laboratoire Interdisciplinaire CARNOT de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon, France
| | - E Hertz
- Laboratoire Interdisciplinaire CARNOT de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon, France
| | - J Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - C Boulet
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Saclay, Orsay F-91405, France
| | - O Faucher
- Laboratoire Interdisciplinaire CARNOT de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon, France
| | - J-M Hartmann
- Laboratoire de Météorologie Dynamique/IPSL, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Sorbonne Université, Ecole Normale Supérieure, Université PSL, F-91120 Palaiseau, France
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Chatterley AS, Baatrup MO, Schouder CA, Stapelfeldt H. Laser-induced alignment dynamics of gas phase CS 2 dimers. Phys Chem Chem Phys 2020; 22:3245-3253. [PMID: 31995073 DOI: 10.1039/c9cp06260b] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Rotational dynamics of gas phase carbon disulfide (CS2) dimers were induced by a moderately intense, circularly polarized alignment laser pulse and measured as a function of time by Coulomb explosion imaging with an intense fs probe pulse. For the alignment pulse, two different temporal intensity profiles were used: a truncated pulse with a 150 ps turn-on and a 8 ps turn-off, or a 'kick' pulse with a duration of 1.3 ps. For both types of pulse, rich rotational dynamics with characteristic full and fractional revivals were recorded, showing that the intermolecular carbon-carbon axis periodically aligns along the propagation direction of the laser pulses. The truncated pulse gave the strongest alignment, which we rationalize as being due to a flat relative phase between the components in the rotational wave packet generated. Fourier analysis of the alignment dynamics gave well-spaced peaks which were fit to determine the rotational constant, B, and the centrifugal constant, DJ, for the ground state of the dimer. Our results agree with values from high-resolution IR spectroscopy. Numerical simulations of the alignment accurately reproduced the experimental dynamics when the truncated pulse or a low intensity kick pulse was used, but failed to reproduce the dynamics induced by a high intensity kick pulse. We posit that the discrepancy is due to excitation of the intermolecular torsional motion by the kick pulse.
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Affiliation(s)
| | - Mia O Baatrup
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - Constant A Schouder
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
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Hartmann JM, Boulet C, Zhang H, Billard F, Faucher O, Lavorel B. Collisional dissipation of the laser-induced alignment of ethane gas: Energy corrected sudden quantum model. J Chem Phys 2018; 149:214305. [PMID: 30525727 DOI: 10.1063/1.5053963] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We present the first quantum mechanical model of the collisional dissipation of the alignment of a gas of symmetric-top molecules (ethane) impulsively induced by a linearly polarized non-resonant laser field. The approach is based on use of the Bloch model and of the Markov and secular approximations in which the effects of collisions are taken into account through the state-to-state rates associated with exchanges among the various rotational states. These rates are constructed using the Energy Corrected Sudden (ECS) approximation with (a few) input parameters obtained independently from fits of the pressure-broadening coefficients of ethane absorption lines. Based on knowledge of the laser pulse characteristics and on these rates, the time-dependent equation driving the evolution of the density matrix during and after the laser pulse is solved and the time dependence of the so-called "alignment factor" is computed. Comparisons with measurements, free of any adjusted parameter, show that the proposed approach leads to good agreement with measurements. The analysis of the ECS state-to-state collisional rates demonstrates that, as in the case of linear molecules, collision-induced changes of the rotational angular momentum orientation are slower than those of its magnitude. This explains why the collisional decay of the permanent component of the alignment is significantly slower than that of the amplitudes of the transient revivals in both experimental and computed results. It is also shown that, since intermolecular forces within C2H6 colliding pairs weakly depend on rotations of the molecules around their C-C bond, the dissipation mechanism of the alignment in pure ethane is close to that involved in linear molecules.
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Affiliation(s)
- J-M Hartmann
- Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École Normale Supérieure, PSL Research University, F-91120 Palaiseau, France
| | - C Boulet
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay F-91405, France
| | - H Zhang
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - F Billard
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - O Faucher
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - B Lavorel
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
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Hartmann JM, Boulet C, Zhang H, Billard F, Faucher O, Lavorel B. Collisional dissipation of the laser-induced alignment of ethane gas: A requantized classical model. J Chem Phys 2018; 149:154301. [PMID: 30342447 DOI: 10.1063/1.5046899] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present the first theoretical study of collisional dissipation of the alignment of a symmetric-top molecule (ethane gas) impulsively induced by a linearly polarized non-resonant laser field. For this, Classical Molecular Dynamics Simulations (CMDSs) are carried out for an ensemble of C2H6 molecules based on knowledge of the laser-pulse characteristics and on an input intermolecular potential. These provide, for a given gas pressure and initial temperature, the orientations of all molecules at all times from which the alignment factor is directly obtained. Comparisons with measurements show that these CMDSs well predict the permanent alignment induced by the laser pulse and its decay with time but, as expected, fail in generating alignment revivals. However, it is shown that introducing a simple requantization procedure in the CMDS "creates" these revivals and that their predicted dissipation decay agrees very well with measured values. The calculations also confirm that, as for linear molecules, the permanent alignment of ethane decays more slowly than the transient revivals. The influence of the intermolecular potential is studied as well as that of the degree of freedom associated with the molecular rotation around the symmetry axis. This reveals that ethane practically behaves as a linear molecule because the intermolecular potential is only weakly sensitive to rotation around the C-C axis.
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Affiliation(s)
- J-M Hartmann
- Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École Normale Supérieure, PSL Research University, F-91120 Palaiseau, France
| | - C Boulet
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay F-91405, France
| | - H Zhang
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université, Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - F Billard
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université, Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - O Faucher
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université, Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - B Lavorel
- Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université, Bourgogne-Franche Comté, 9 Ave. A. Savary, BP 47 870, F-21078 Dijon Cedex, France
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