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The infrared-driven cis-trans isomerization of nitrous acid HONO III: a mixed quantum–classical simulation


Hamm, P (2008). The infrared-driven cis-trans isomerization of nitrous acid HONO III: a mixed quantum–classical simulation. Chemical Physics, 347(1-3):503-513.

Abstract

A mixed quantum-classical simulation of the IR-driven cis-trans isomerization of HONO in a Kr matrix at 30 K is presented, treating the hydrogen atom as quantum particle and the Kr matrix as well as intermolecular degrees of freedom of the ONO-body as classical. A new method is presented to time-propagate the coupled set of equations in a DVR basis in internal spherical coordinates, rather than in laboratory frame fixed cartesian coordinates. In spherical coordinates, a much more precise computation of the weak vibrational couplings is possible using a still manageable basis size. Good qualitative agreement between simulation and experiment is obtained, underestimating relaxation and isomerization rates by a modest factor approximate to 5. Upon matrix fluctuations, frequent curve crossings occur between the initially excited OH-stretch vibration and a closely lying combination mode of torsional and bending coordinate that lead to a transfer of population. The subsequent pathway of energy flow is deduced and discussed within a tier model, where trans-states, that belong to the second tier, are populated through a first tier of states that is composed of combinations of bending and torsional excitations. No specific energy pathway is revealed that would funnel the hydrogen atom directly towards the trans-side, hence the experimentally observed high cis -> trans quantum yield of close to one probably has to be explained in a statistical scenario on a timescale much longer than that of the present simulation. (C) 2007 Elsevier B.V. All rights reserved.

A mixed quantum-classical simulation of the IR-driven cis-trans isomerization of HONO in a Kr matrix at 30 K is presented, treating the hydrogen atom as quantum particle and the Kr matrix as well as intermolecular degrees of freedom of the ONO-body as classical. A new method is presented to time-propagate the coupled set of equations in a DVR basis in internal spherical coordinates, rather than in laboratory frame fixed cartesian coordinates. In spherical coordinates, a much more precise computation of the weak vibrational couplings is possible using a still manageable basis size. Good qualitative agreement between simulation and experiment is obtained, underestimating relaxation and isomerization rates by a modest factor approximate to 5. Upon matrix fluctuations, frequent curve crossings occur between the initially excited OH-stretch vibration and a closely lying combination mode of torsional and bending coordinate that lead to a transfer of population. The subsequent pathway of energy flow is deduced and discussed within a tier model, where trans-states, that belong to the second tier, are populated through a first tier of states that is composed of combinations of bending and torsional excitations. No specific energy pathway is revealed that would funnel the hydrogen atom directly towards the trans-side, hence the experimentally observed high cis -> trans quantum yield of close to one probably has to be explained in a statistical scenario on a timescale much longer than that of the present simulation. (C) 2007 Elsevier B.V. All rights reserved.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:23 May 2008
Deposited On:15 Jan 2009 12:20
Last Modified:05 Apr 2016 12:44
Publisher:Elsevier
ISSN:0301-0104
Publisher DOI:10.1016/j.chemphys.2007.10.013
Permanent URL: http://doi.org/10.5167/uzh-8677

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