The photodissociation of jet cooled benzyl radicals, C7H7, at 248 nm has been studied using photofragment translational spectroscopy. Two dissociation channels were observed, H + C7H6 and CH3 + C6H4. The translational energy distribution determined for each channel suggests that both dissociation mechanisms occur via internal conversion to the ground state followed by intramolecular vibrational redistribution and dissociation. The branching ratio between these two channels has been measured to be (CH3 + C6H4)/(H + C7H6) = 0.011 ± 0.004. The dominance of the H + C7H6 channel is corroborated by the branching ratio calculated using Rice-Ramsperger-Kassel-Marcus theory.

Photofragment translational spectroscopy was used to study the photodissociation of fulvenallene, CH, and the fulvenallenyl radical, CH, at 248 nm and 193 nm. Starting from fulvenallene, only the H-atom loss channel producing the fulvenallenyl radical, CH, was observed. Fulvenallene dissociation occurs on the ground state surface with no exit barrier, and there is good agreement between our experimentally determined photofragment translational energy distribution and a prior distribution for a statistical process. Subsequent absorption at both wavelengths by fulvenallenyl enabled investigation of the photodissociation of this radical. Two channels were observed: CH + CH and CH + CH. The photofragment translational energy distributions for these channels are peaked away from 0 kcal mol, which is consistent with ground state dissociation over an exit barrier. At 248 nm, the CH-loss channel accounted for 85 ± 10% of fulvenallenyl dissociation, while at 193 nm it accounted for 80 ± 15%. The experimental branching between these channels is in reasonable agreement with Rice-Ramsperger-Kassel-Marcus theory calculations, which predict CH-loss to account for 70% and 63% of dissociation for 248 nm and 193 nm respectively.