Observation of Nonradiative Processes in Benzene Vapor by Photoacoustic Spectroscopy

A photoacoustic (PA) and an absorption spectra of benzene vapor have been measured in the wavelength region from 280 to 220 nm. We determined nonradiative yields at the absorption peaks. We found that the relaxation process of benzene vapor at the wavelengths shorter than 242 nm, whose process has been called the third channel, is a nonradiative relaxation process with temperature rise of the benzene vapor. We also observed a drastic decrease of the nonradiative yields at wavelengths shorter than 233 nm, which seems to suggest an increase of quantum yield for photochemical isomerization.