RESONANCE IONIZATION SPECTROSCOPY OF MOLECULAR CLUSTER USING PICOSECOND LASERS

High peak-power picosecond laser pulses have been used for the first time to effect nonresonant or resonant multiphoton ionization (MPI) of clusters generated in a supersonic nozzle expansion. The resultant ions are subsequently detected and characterized by time-of-flight mass spectroscopy. Specifically, we present results involving MPI of the cluster series Ar(n)NO, (NO)n, and Ar(n)I2. Previous MPI studies of the latter two species using nanosecond lasers have not been successful in detecting the parent ion, presumably due to fast dissociation channels. It is proposed that the present technique is a new and rather general ionization source for cluster studies which is complementary to electron impact but in addition, may provide unique spectroscopic or dynamical information.