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The role of electronically excited states in recombination reactions
Author(s) -
Smith Ian W. M.
Publication year - 1984
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550160411
Subject(s) - excited state , degeneracy (biology) , chemistry , atomic physics , ab initio , bound state , electronic structure , ab initio quantum chemistry methods , molecular physics , physics , computational chemistry , quantum mechanics , molecule , bioinformatics , organic chemistry , biology
Methods are described for including the participation of bound electronically excited states in calculations on radical recombination reactions. These methods are illustrated by applying them to the reactions\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O}\left( {^{\rm 3} P} \right)\,\, + \,{\rm O}\left( {^{\rm 3} P} \right)\,\, + \,\,{\rm M} \to {\rm O}_{{\rm 2}\,} \,\, + \,\,{\rm M}\,} \\ {{\rm O}\left( {^{\rm 3} P} \right)\,\,\, + \,\,{\rm NO}\left( {{\rm X}^{\rm 2} {\rm II}} \right)\, + \,\,{\rm M} \to {\rm NO}_{{\rm 2}\,} \,\, + \,\,{\rm M}} \\ {{\rm OH}\left( {{\rm X}^{\rm 2} {\rm II}} \right)\,\, + \,\,{\rm NO}_{\rm 2} \left( {\tilde X^2 A_1 } \right)\, + \,\,{\rm M} \to {\rm HNO}_{3\,} \,\, + \,\,{\rm M}\,\,\,} \\ \end{array} $$\end{document}For O 2 , accurate ab initio potentials are used in calculations which show that the electronic degeneracy and long‐range part of the potential are likely to be crucial in determining the contribution of a given electronic state to the overall reaction, as long as the state is not so weakly bound that it dissociates thermally before being electronically quenched. Weak collision effects are allowed for using a Monte Carlo technique and an assumed exponential form for the distribution of energies transferred in collisions with a third body. For larger systems it is evident that the role of bound excited states in the low‐pressure regime falls rapidly as the size of the system increases. As the high‐pressure limit is approached, however, the contribution of excited states is likely to come close to that expected simply on the basis of electronic degeneracy.