Photodissociation of Bromoform at 248 nm: Single and Multiphoton Processes

Abstract

We have performed photodissociation experiments on CHBr3 at 248 nm using VUV ionization photofragment translational spectroscopy. Prompt C−Br bond fission is the dominant single-photon dissociation channel. In addition to primary Br and CHBr2 signals, we observe Br, CHBr, CBr, HBr, and Br2 products attributed to secondary photodissociation of CHBr2 and CHBr. There are three competing fragmentation channels from the photodissociation of CHBr2: CHBr + Br, CH + Br2, and CBr + HBr. The conclusion that Br2 fragments do not arise from a single-photon channel in appreciable yield is supported by transient FM absorption measurements of the CHBr radical. Because the molecular HBr and Br2 detachment channels are multiphoton processes, they will have very little impact on the atmospheric chemistry of CHBr3. We conclude that the most important photodissociation channel of CHBr3 in the UV region is C−Br bond breaking.