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Vibrational Energy Transfer in CO+N₂ Collisions: A Database for V-V and V-T/R Quantum-Classical Rate Coefficients.

ABSTRACT: Knowledge of energy exchange rate constants in inelastic collisions is critically required for accurate characterization and simulation of several processes in gaseous environments, including planetary atmospheres, plasma, combustion, etc. Determination of these rate constants requires accurate potential energy surfaces (PESs) that describe in detail the full interaction region space and the use of collision dynamics methods capable of including the most relevant quantum effects. In this work, we produce an extensive collection of vibration-to-vibration (V-V) and vibration-to-translation/rotation (V-T/R) energy transfer rate coefficients for collisions between CO and N2 molecules using a mixed quantum-classical method and a recently introduced (A. Lombardi, F. Pirani, M. Bartolomei, C. Coletti, and A. Laganà, Frontiers in chemistry, 7, 309 (2019)) analytical PES, critically revised to improve its performance against ab initio and experimental data of different sources. The present database gives a good agreement with available experimental values of V-V rate coefficients and covers an unprecedented number of transitions and a wide range of temperatures. Furthermore, this is the first database of V-T/R rate coefficients for the title collisions. These processes are shown to often be the most probable ones at high temperatures and/or for highly excited molecules, such conditions being relevant in the modeling of hypersonic flows, plasma, and aerospace applications.

SUBMITTER: Hong Q

PROVIDER: S-EPMC8659027 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We report state-resolved total removal cross sections and state-to-state rotational energy transfer (RET) cross sections for collisions of CN(A(2)Π, ν = 4, j F1ε) with N2, O2, and CO2. CN(X(2)Σ(+)) was produced by 266 nm photolysis of ICN in a thermal bath (296 K) of the collider gas. A circularly polarized pulse from a dye laser prepared CN(A(2)Π, ν = 4) in a range of F1e rotational states, j = 2.5, 3.5, 6.5, 11.5, 13.5, and 18.5. These prepared states were monitored using the circularly polarized output of an external cavity diode laser by frequency-modulated (FM) spectroscopy on the CN(A-X)(4,2) band. The FM Doppler profiles were analyzed as a function of pump-probe delay to determine the time dependence of the population of the initially prepared states. Kinetic analysis of the resulting time dependences was used to determine total removal cross sections from the initially prepared levels. In addition, a range of j' F1e and j' F2f product states resulting from rotational energy transfer out of the j = 6.5 F1e initial state were probed, from which state-to-state RET cross sections were measured. The total removal cross sections lie in the order CO2 > N2 > O2, with evidence for substantial cross sections for electronic and/or reactive quenching of CN(A, ν = 4) to unobserved products with CO2 and O2. This is supported by the magnitude of the state-to-state RET cross sections, where a deficit of transferred population is apparent for CO2 and O2. A strong propensity for conservation of rotational parity in RET is observed for all three colliders. Spin-orbit-changing cross sections are approximately half of those of the respective conserving cross sections. These results are in marked disagreement with previous experimental observations with N2 as a collider but are in good agreement with quantum scattering calculations from the same study ( Khachatrian et al. J. Phys. Chem. A 2009 , 113 , 3922 ). Our results with CO2 as a collider are similarly in strong disagreement with a related experimental study ( Khachatrian et al. J. Phys. Chem. A 2009 , 113 , 13390 ). We therefore propose that the previous experiments substantially underestimated the spin-orbit-changing cross sections for collisions with both N2 and CO2, suggesting that even approximate quantum scattering calculations may be more successful for such molecule-molecule systems than was previously concluded.

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Vibrational Energy Transfer in CO+N₂ Collisions: A Database for V-V and V-T/R Quantum-Classical Rate Coefficients.

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Vibrational Energy Transfer in CO+N2 Collisions: A Database for V-V and V-T/R Quantum-Classical Rate Coefficients.

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OmicsDI is part of the ELIXIR infrastructure

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Vibrational Energy Transfer in CO+N₂ Collisions: A Database for V-V and V-T/R Quantum-Classical Rate Coefficients.