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Title: Vibrational mode and collision energy effects on reaction of H{sub 2}CO{sup +} with C{sub 2}H{sub 2}: Charge state competition and the role of Franck-Condon factors in endoergic charge transfer

The effects of collision energy (E{sub col}) and six different H{sub 2}CO{sup +} vibrational states on the title reaction have been studied over the center-of-mass E{sub col} range from 0.1 to 2.6 eV, including measurements of product ion recoil velocity distributions. Ab initio and Rice-Ramsperger-Kassel-Marcus calculations were used to examine the properties of complexes and transition states that might be important in mediating the reaction. Reaction is largely direct, despite the presence of multiple deep wells on the potential surface. Five product channels are observed, with a total reaction cross section at the collision limit. The competition among the major H{sub 2}{sup +} transfer, hydrogen transfer, and proton transfer channels is strongly affected by E{sub col} and H{sub 2}CO{sup +} vibrational excitation, providing insight into the factors that control competition and charge state 'unmixing' during product separation. One of the more interesting results is that endoergic charge transfer appears to be controlled by Franck-Condon factors, implying that it occurs at large inter-reactant separations, contrary to the expectation that endoergic reactions should require intimate collisions to drive the necessary energy conversion.
Authors:
; ;  [1]
  1. Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 (United States)
Publication Date:
OSTI Identifier:
20723273
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 123; Journal Issue: 20; Other Information: DOI: 10.1063/1.2128670; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ACETYLENE; CENTER-OF-MASS SYSTEM; CHARGE EXCHANGE; CHARGE STATES; COMPLEXES; ENERGY CONVERSION; EV RANGE 01-10; EXCITATION; HYDROGEN IONS 2 PLUS; HYDROGEN TRANSFER; ION-MOLECULE COLLISIONS; MILLI EV RANGE; PROTONS; REACTION KINETICS; SURFACES; VIBRATIONAL STATES