On the dynamics of the xylene isomers excited in the VUV region.

We report on the dynamics of electronically excited o-, m-, and p-xylene on the femtosecond timescale by employing the vacuum-ultraviolet pump-IR probe mass spectrometry technique. The molecules were excited by the fifth harmonic (=160nm) of a Ti:sapphire laser at a superposition of the S-3 valence with several Rydberg states. The relaxation pathways were investigated by studying the parent P+ and the fragment [P-H](+) and [P-CH3](+) time-resolved signals generated after interaction with the fundamental beam (=800nm). Relaxation from the excited valence states was found to depend on the relative positions of the methyl groups on the ring. An increasing trend in the order oMore