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Equilibration of vibrationally excited OH in atomic and diatomic bath gases

journal contribution
posted on 2023-06-08, 09:54 authored by Anthony J McCaffery, Marisian Pritchard, John TurnerJohn Turner, Richard J Marsh
In this work, a computational model of state-to-state energy flow in gas ensembles is used to investigate collisional relaxation of excited OH, present as a minor species in various bath gases. Rovibrational quantum state populations are computed for each component species in ensembles consisting of 8000 molecules undergoing cycles of binary collisions. Results are presented as quantum state populations and as (approximate) modal temperatures for each species after each collision cycle. Equilibration of OH is slow with Ar as the partner but much faster when N2 and/or O2 forms the bath gas. This accelerated thermalization is shown to be the result of near-resonant vibration-vibration transfer, with vibrational de-excitation in OH matched in energy by excitation in bath molecules. Successive near-resonant events result in an energy cascade. Such processes are highly dependent on molecule pair and on initial OH vibrational state. OH rotational temperatures initially increase, but at equilibration, they are lower than those of other modes. Possible reasons for this observation in molecules such as OH are suggested. There are indications of an order of precedent in the equilibration process, with vibrations taking priority over rotations, and potential explanations for this phenomenon are discussed.

History

Publication status

  • Published

Journal

Journal of Physical Chemistry A

ISSN

1089-5639

Publisher

ACS Publications

Issue

17

Volume

115

Page range

4169-4178

Department affiliated with

  • Chemistry Publications

Notes

Anthony J. McCaffery Marisian Pritchard and Richard J. Marsh

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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