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Title: Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm

Abstract

This paper presents velocity and angular distribution measurements of the products of N{sub 2}O{sub 4} photodissociated at 193 nm. The data show evidence for only N-N bond fission, with no significant branching to N-O bond fission or NO elimination products. The translational energy distribution of the N-N bond fission products is bimodal, indicating that at least two different NO{sub 2} + NO{sub 2} product channels contribute significantly to the observed products. Both product channels have an anisotropy parameter of {beta} = 1.7 {+-} 0.2. Using a Franck-Condon-like sudden analysis, the authors tentatively assign the two fragmentation channels observed as NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) and NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(2{sup 2}B{sub 2}). To further characterize the system the authors present ab initio calculations (at the level of configuration interaction with single excitations) of the relevant excites states of N{sub 2}O{sub 4}. The data considered together with the calculations suggest a model for the product branching in which there is spin-orbit coupling in the Franck-Condon region between the excited state, which has mixed singlet {pi}{pi}* and n{sigma}* character, and a state with {sup 3}{pi}{sigma}* character. Branching to the NO{sub 2}({tilde X})more » + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) channel occurs upon intersystem crossing to the triplet surface, and formation of the {pi}{pi}* diabatic products NO{sub 2}(X) + NO{sub 2}(2{sup 2}B{sub 2}) occurs from the singlet {pi}{pi}* state nonadiabatic dynamics. Finally, the authors note that the observed parallel photofragment anisotropy, unexpected for {pi}{pi}* electronic excitation of N{sub 2}O{sub 4}, likely results from vibronic coupling with a {sigma}{sigma}* electronic state.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Chicago, IL (US)
OSTI Identifier:
20075883
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 104; Journal Issue: 21; Other Information: PBD: 1 Jun 2000; Journal ID: ISSN 1089-5639
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ATMOSPHERIC CHEMISTRY; NITROGEN OXIDES; DISSOCIATION; PHOTOCHEMISTRY; MATHEMATICAL MODELS; L-S COUPLING; ANISOTROPY

Citation Formats

Mueller, J.A., Morton, M.L., Curry, S.L., Abbatt, J.P.D., and Butler, L.J. Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm. United States: N. p., 2000. Web. doi:10.1021/jp993651u.
Mueller, J.A., Morton, M.L., Curry, S.L., Abbatt, J.P.D., & Butler, L.J. Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm. United States. doi:10.1021/jp993651u.
Mueller, J.A., Morton, M.L., Curry, S.L., Abbatt, J.P.D., and Butler, L.J. Thu . "Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm". United States. doi:10.1021/jp993651u.
@article{osti_20075883,
title = {Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm},
author = {Mueller, J.A. and Morton, M.L. and Curry, S.L. and Abbatt, J.P.D. and Butler, L.J.},
abstractNote = {This paper presents velocity and angular distribution measurements of the products of N{sub 2}O{sub 4} photodissociated at 193 nm. The data show evidence for only N-N bond fission, with no significant branching to N-O bond fission or NO elimination products. The translational energy distribution of the N-N bond fission products is bimodal, indicating that at least two different NO{sub 2} + NO{sub 2} product channels contribute significantly to the observed products. Both product channels have an anisotropy parameter of {beta} = 1.7 {+-} 0.2. Using a Franck-Condon-like sudden analysis, the authors tentatively assign the two fragmentation channels observed as NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) and NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(2{sup 2}B{sub 2}). To further characterize the system the authors present ab initio calculations (at the level of configuration interaction with single excitations) of the relevant excites states of N{sub 2}O{sub 4}. The data considered together with the calculations suggest a model for the product branching in which there is spin-orbit coupling in the Franck-Condon region between the excited state, which has mixed singlet {pi}{pi}* and n{sigma}* character, and a state with {sup 3}{pi}{sigma}* character. Branching to the NO{sub 2}({tilde X}) + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) channel occurs upon intersystem crossing to the triplet surface, and formation of the {pi}{pi}* diabatic products NO{sub 2}(X) + NO{sub 2}(2{sup 2}B{sub 2}) occurs from the singlet {pi}{pi}* state nonadiabatic dynamics. Finally, the authors note that the observed parallel photofragment anisotropy, unexpected for {pi}{pi}* electronic excitation of N{sub 2}O{sub 4}, likely results from vibronic coupling with a {sigma}{sigma}* electronic state.},
doi = {10.1021/jp993651u},
journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
issn = {1089-5639},
number = 21,
volume = 104,
place = {United States},
year = {2000},
month = {6}
}