Primary and secondary processes in the photodissociation of CHBr3

The photodissociation of CHBr3 at 193 nm has been investigated using photof ragment translational spectroscopy with VUV ionization detection. The only primary process observed was the loss of bromine atom. The translational en ergy distribution for this channel suggests a direct dissociation from an e xcited electronic state, and the anisotropy parameter, beta = 0.0, is consi stent with a transition dipole moment aligned perpendicular to the C-3v axi s. The majority of nascent CHBr2 fragments undergo secondary dissociation v ia two competing channels. The elimination of HBr and C-Br bond cleavage in CHBr2 occur with comparable yields. We also provide ab initio calculations on the relevant photochemical species and RRKM estimates of the product br anching ratios that are consistent with the experimental observations.