Fluorescence from High Vibronically Excited Benzene: a "Channel Three" Problem

Abstract

Gas phase benzene is excited by two-photon absorption at various pressures between 4 and 80 torr. Fluorescence is observed even from states located at excess energies of 3000 cm^-1 - 7000 cm^-1 , i.e. well above the onset of "channel three". The nonradiative decay rates as estimated from this fluorescence intensity continue the well known shortening of lifetime with excess energy in a monotone fashion and do not show a drastic cut-off as often concluded from previous line-width measurements.