Photodissociation dynamics of xylene isomers C6H4(CH3)2 at 157 nm using an ultracompact velocity map imaging spectrometer – The C7H7 channel

Abstract

We investigated the photodissociation dynamics of three xylene isomers C6H4(CH3)2 at 157 nm. The center-of-mass translational energy distributions of C7H7 radicals were found to peak at 26 kJ mol−1. Although the ionization energy of the C7H7 tolyl fragment exceeds the energy of a 157 nm photon, C7H7+ was observed as a result of the photoionization of vibrationally ‘hot’ tolyl (C7H7) radicals and/or two-photon ionization. The formation of rovibrationally excited tolyl fragments was discussed. Our experiments suggest the presence of tolyl radicals in the interstellar medium as a precursor to methylated polycyclic aromatic hydrocarbons upon reaction with vinylacetylene (C4H4).