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

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 for-mation 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).

Automated summary

We investigated the photodissociation dynamics of three xylene isomers C6H4(CH3)2 at 157 nm. We found that the center-of-mass translational energy distributions of C7H7 radicals peaked at 26 kJ mol-1. Despite the ionization energy of the C7H7 tolyl fragment being higher than the energy of a 157 nm photon, the formation of C7H7+ was observed due to the photoionization of vibrationally 'hot' tolyl (C7H7) radicals and/or two-photon ionization. Our experiments suggest the presence of tolyl radicals in the interstellar medium as precursors to methylated polycyclic aromatic hydrocarbons.