Low-energy electron collisions with CH₃Br: the dependence of elastic scattering, vibrational excitation, and dissociative attachment on the initial vibrational energy

Authors

M. Braun, Fachbereich Physik, Technische Universität Kaiserslautern, D-67653 Kaiserslautern, Germany
Ilya I. Fabrikant, University of Nebraska-LincolnFollow
M-W. Ruf, University of Nebraska-Lincoln
H. Hotop, University of Nebraska-LincolnFollow

Date of this Version

1-26-2007

Comments

Published in Journal of Physics B: Atomic, Molecular and Optical Physics 40 (2007), pp. 659–674. Online at http://stacks.iop.org/JPhysB/40/659. Copyright © 2007 IOP Publishing Ltd. Used by permission.

Abstract

Using the laser photoelectron attachment (LPA) method at an energy width of 1–2 meV, the Br^- yield due to dissociative electron attachment to the molecule CH₃Br has been measured over the energy range 1–180 meV at a gas temperature of 600 K. The data clearly exhibit the vibrational Feshbach resonance predicted by Wilde et al. (2000 J. Phys. B: At. Mol. Opt. Phys. 33 5479) and associated with the v₃ = 4 vibrational level of the C–Br stretch mode in the neutral molecule. We also report the dependence of the rate coefficient for Rydberg electron attachment (measured at high principal quantum numbers n ≈ 150) on gas temperature and find an Arrhenius-type behavior compatible with the results of R-matrix calculations and with earlier findings of electron swarm experiments. With the aim to stimulate experiments, we report absolute cross sections for elastic scattering and vibrationally inelastic scattering involving the C–Br stretch mode v₃ of CH₃Br for several initial vibrational levels in the range v₃ = 0–4; they were obtained with R-matrix calculations based on the same potential input as that involved in the computations of the cross sections for dissociative attachment.