Formation of benzene dimer cations in neat liquid benzene studied by femtosecond transient absorption spectroscopy

Photoionization of neat liquid benzene has been studied by femtosecond pump-probe experiments in the near infrared region. A transient species is formed within 1 ps following two-photon excitation of liquid benzene at 268 nm, which shows a broad absorption band with a peak at 920 nm and extended intensities at wavelengths longer than 1000 nm. This band is attributed to a charge resonance band of a localized benzene dimer cation. The transient species show essentially no evidence of the recombination with electrons in a time shorter than 50 ps.