Hyperthermal reactions of O +( 4S 3/2) with CD 4 and CH 4: Theory and experiment

Dale J. Levandier, Yu Hui Chiu, Rainer A. Dressler, Lipeng Sun, George C. Schatz

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Abstract

Theoretical and experimental methods are applied to the study of the reaction dynamics in hyperthermal collisions of O + ( 4S 3/2) with methane. Measurements of the absolute reaction cross sections for the interaction of O + with CD 4 and CH 4 were obtained at collision energies in the range from near-thermal to approximately 15 eV, using the guided-ion beam (GIB) technique. Product recoil velocity distributions, using the GIB time-of-flight (TOF) methods, were determined for several product ions at selected collision energies. The main reaction channel, charge transfer, proceeds via large impact parameter collisions. A number of minor channels, involving more intimate collisions, were also detected. Ab initio electronic structure calculations have been performed with different levels of theory and basis sets, including high-level coupled-cluster calculations to determine the energies of reaction intermediates and transition states for reaction. Several reaction paths on both quartet and doublet electronic states of (O·CH 4) + are found, and these provide a reasonable qualitative interpretation of the experiments. Although most of the products can be produced via spin-allowed pathways, the appearance of CH 3 + at low energies suggests that intersystem crossing plays some role.

Original languageEnglish
Pages (from-to)9794-9804
Number of pages11
JournalJournal of Physical Chemistry A
Volume108
Issue number45
DOIs
Publication statusPublished - Nov 11 2004

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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