On the “third decay channel” and vibrational redistribution problems in benzene derivatives

Fluorescence lifetimes and yields have been measured for toluene, aniline-h₇ and aniline-d₅ vapors in the spectral range corresponding to a rapid increase of the non-radiative rates. Non-exponential decays and discrepancies between lifetime and yield dependence on ν_exc are observed. Results are discussed on the ground of a model assuming: (a) strong anharmonic coupling of “active” and “non-active” modes, (b) specific “third channel” threshold for each vibrational progression and (c) absence of rapid vibrational redistribution.