Dissociation Dynamics of Isotopologs of CH5 Studied by Charge Exchange of CH5+ with Cs and Quasiclassical Trajectory Calculations

Abstract

The product branching fractions and dissociation dynamics for the dissociation of CH₅, CH₂D₃, CHD₄, and CD₅ have been experimentally measured following charge exchange of the parent cations with Cs. These results are compared with quasiclassical trajectory calculations run on an ab initio potential energy surface for CH₅. In all cases it is found that dissociation channels involving the ejection of a single atom (H or D) are dominant. The statistically weighted branching fractions show that in the mixed isotopologs, ejection of a hydrogen atom is favored over a deuterium atom. The results are consistent with the fluxional nature of CH₅(+) isotopologs--no evidence was found for quantum localization upon deuteration in the comparison of the experimental and theoretical branching fractions, possibly as a result of the vibrational temperature of the cations (estimated to be as high as 1660 K for high frequency modes). This comparison of experiment and theory provides a test of the CH₅ potential energy surface at high levels of excitation.