Changeable behavior in the unimolecular decay channels of electronically excited states of methyl bromide(1+) and methyl chloride(1+)

Fragmentation of the first and second electronically excited states of methyl chloride and bromide cations has been studied, the ground state of each molecular ion being stable to dissociation. Product branching ratios and kinetic energy release upon dissociation were investigated using He I photoelectron-photoion coincidence (PEPICO) measurements. The principal fragmentation of the excited states is a C-X bond cleavage. Both excited states of the ion CH 3 Br + follow essentially statistical routes in this channel, though small deviations from a fully randomized distribution are noted and these become more marked for vibrationally excited A-state parent