Ultrafast internal conversion of benzene and toluene from the S2 states was studied by time-resolved photoelectron imaging with a time resolution of 22 fs. Time-energy maps of the photoelectron intensity and the angular anisotropy were generated from a series of photoelectron images. The photoelectron kinetic energy distribution exhibits a rapid energy shift and intensity revival, which indicates nuclear motion on the S2 adiabatic surface, while the ultrafast evolution of the angular anisotropy revealed a change in the electronic character of the S2 adiabatic surface. From their decay profiles of the total photoelectron intensity, the time constants of 48 ± 4 and 62 ± 4 fs were determined for the population decay from the S2 states in benzene and toluene, respectively.
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