Internal conversion in highly excited benzene and benzene dimer: femtosecond time-resolved photoelectron spectroscopy

Photoelectron spectra of benzene molecules and dimers excited to the S2 electronic state by 140 fs laser pulses at a wavelength of 200 nm have been measured by combining the pump–probe technique with the coincidence detection of ions and electrons. Their time dependence allows one to directly follow the evolution of internal conversion processes in different electronic states on a fs time-scale. Analysis of the corresponding electron energy distribution reveals large variations in the geometry of the different electronic states in both benzene and in its dimer.