State selected ion–molecule reactions by a TESICO technique. VIII. Vibronic-state dependence of the cross sections in the reaction NO+(a 3Σ+, v ; b 3Π, v)+Ar → NO+Ar+

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Abstract
Charge transfer reactions NO++Ar → Ar++NO (1) have been studied by selecting the vibronic states of NO+ using the threshold electron–secondary ion coincidence (TESICO) technique. The vibronic states selected were a 3Σ+, v=0–5 and b 3Π, v=0, for each of which the relative cross sections have been determined at two collision energies 1.4 and 5.8 eV. The cross section for the a 3Σ+ state has been found to show a resonancelike enhancement at v=2. This feature is reproduced fairly well by the simple two‐state theory of Rapp and Francis combined with the consideration of the Franck–Condon factors. However, a closer comparison of the theoretical and experimental results over the entire range of v reveals that the reaction cross sections for the a 3Σ+ reactant ion state consist of two components, one in which the vibrational‐state dependence is determined simply by the energy defects and Franck–Condon factors, and the other in which the vibrational‐state dependence cannot be interpreted by those factors. The cross section for the b 3Π, v=0 state has been found to be much smaller than those for the exoergic reactions of the a 3Σ+ state (v=1–5). This has been attributed to the difference in the nature of the molecular orbitals that play primary roles in the a 3Σ+ and b 3Π reactions.

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