Picosecond IR-UV pump-probe spectroscopy. IVR of OH stretching vibration of phenol and phenol dimer

Intramolecular and intracluster vibrational energy redistribution (IVR) fro m OH stretching vibrations of phenol and phenol dimer have been investigate d for the first time by picosecond time-resolved IR-UV pump-probe spectrosc opy. The OH stretching level was pumped by a picosecond IR laser pulse and the decay of the pumped level as well as appearance of the energy redistrib uted vibrational levels was observed using resonance enhanced multiphoton i onization scheme with a picosecond UV laser. For bare phenol, IVR of the OH stretching level was found to occur with a lifetime of 14 ps. For the dime r, a remarkable site-dependence was observed for the IVR lifetime of the OH stretching level; IVR of the proton-donating site occurs less than 5 ps, w hile that of the proton accepting site occurs with 14 ps. comparable to tha t of bare phenol. In the case of a cluster, IVR was followed by vibrational predissociation, which occurs with lifetimes of several tens of picosecond s.