Development of picosecond IR-UV pump probe spectroscopy for molecular clusters

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An experimental setup for the picosecond IR-UV double resonance spectroscopy has been constructed. The setup was developed to study the vibrational relaxation of molecular clusters formed in a supersonic beam. The setup consists of a mode-locked picosecond Nd:YAG laser and an opto-parametric system. A fundamental of the Nd:YAG laser is converted to 3 μm by OPG with the use of nonlinear crystal, which is used to pump the clusters to the CH or OH stretching vibration. A picosecond tunable UV light was also generated by the OPG system, which is used to monitor the vibratinally excited clusters by resonant enhance ionization. The two laser pulses were irradiated to the clusters in the supersonic beam. By changing the delay time between the IR and the UV pulses, the time profiles of the vibratinally excited states were monitored. It was found that the OH stretching vibration of phenol is 15 picoseconds and those its clusters are much faster.