Picosecond IR−UV Pump−Probe Spectroscopy. IVR of OH Stretching Vibration of Phenol and Phenol Dimer

Abstract

Intramolecular and intracluster vibrational energy redistribution(IVR) from OH stretching vibrations of phenol and phenol dimer have been investigated for the first time by picosecond time-resolved IR−UV pump−probe spectroscopy. 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 redistributed vibrational levels was observed using resonance enhanced multiphoton ionization 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 dimer, 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, while that of the proton accepting site occurs with 14 ps, comparable to that of bare phenol. In the case of a cluster, IVR was followed by vibrational predissociation, which occurs with lifetimes of several tens of picoseconds.