UV photodissociation of methyl bromide and methyl bromide cation studied by velocity map imaging

TL;DR

This study uses velocity map imaging to analyze the photodissociation of methyl bromide at 215.9 nm, revealing detailed kinetic and angular distributions of fragments and vibrational excitations, with implications for understanding dissociation dynamics.

Contribution

It provides the first detailed velocity map imaging analysis of methyl bromide photodissociation at this wavelength, highlighting vibrational differences in fragments and structured features near 330 nm.

Findings

Different vibrational excitations for Br and Br* channels.

Structured features indicating energy distribution in fragments.

Excess energy channels into methyl vibrational modes.

Abstract

We employ the velocity map imaging technique to measure kinetic energy and angular distributions of state selected CH3 (v2=0,1,2,3) and Br (2P3/2,2P1/2) photofragments produced by methyl bromide photolysis at 215.9 nm. These results show unambiguously that the Br and Br* forming channels result in different vibrational excitation of the umbrella mode of the methyl fragment. Low energy structured features appear on the images which arise from CH3Br+ photodissociation near 330 nm. The excess energy of the probe laser photon is channeled into CH3+ vibrational excitation, most probably in the nu_4 degenerate bend