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Modelling collisional energy transfer in highly excited molecules

Version 2 2024-06-03, 09:50
Version 1 2015-08-21, 11:50
journal contribution
posted on 2024-06-03, 09:50 authored by Kieran LimKieran Lim, RG Gilbert
Data from classical trajectory simulations of the collision of a highly excited molecule with a monatomic bath gas are used to test the validity of the precepts used in the biased-random-walk (BRW) model for collisional energy transfer. This model assumes that energy migration during the collision is pseudorandom except for the constraint of microscopic reversibility, and leads to a simple displaced Gaussian form for the energy-transfer probability distribution. The BRW assumptions are shown to be of acceptable validity to exact classical trajectory simulations. A simple analytical approximation to the mean-square energy transfer per collision is obtained which reproduces the trajectory data to within an average of ±20%, and also gives acceptable accord with experimental data. The model shows that the magnitude of the average energy transferred per collision is governed by the time taken to traverse the overall interaction potential in and out from the appropriate collision diameter, by the internal energy, and by the average force exerted at the classical turning point of individual reactant-atom–bath-gas interactions.

History

Journal

Journal of Chemical Physics

Volume

92

Pagination

1819-1830

ISSN

0021-9606

Notes

Data from classical trajectory simulations of the collision of a highly excited molecule with a monatomic bath gas are used to test the validity of the precepts used in the biased-random-walk (BRW) model for collisional energy transfer. This model assumes that energy migration during the collision is pseudorandom except for the constraint of microscopic reversibility, and leads to a simple displaced Gaussian form for the energy-transfer probability distribution. The BRW assumptions are shown to be of acceptable validity to exact classical trajectory simulations. A simple analytical approximation to the mean-square energy transfer per collision is obtained which reproduces the trajectory data to within an average of ±20%, and also gives acceptable accord with experimental data. The model shows that the magnitude of the average energy transferred per collision is governed by the time taken to traverse the overall interaction potential in and out from the appropriate collision diameter, by the internal energy, and by the average force exerted at the classical turning point of individual reactant-atom–bath-gas interactions.

Publication classification

CN.1 Other journal article

Copyright notice

1990, AIP Publishing

Issue

3

Publisher

AIP Publishing

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