TIME-RESOLVED STUDIES OF NEUTRAL AND IONIZED NA(N) CLUSTERS WITH FEMTOSECOND LIGHT-PULSES

The real-time dynamics of Na(n) (n=3-21) cluster multiphoton ionization and fragmentation has been studied in beam experiments applying femtosecond pump-probe techniques in combination with ion and electron spectroscopy. Three dimensional wave packet motions in the trimer Na3 ground state X and excited state B have been observed. We report the first study of cluster properties (energy, bandwidth and lifetime of intermediate resonances Na(n)*) with femtosecond laser pulses. The observation of four absorption resonances for the cluster Na8 with different energy widths and different decay patterns is more difficult to interpret by surface plasmon like resonances than by molecular structure and dynamics. Time-resolved fragmentation of cluster ions Na(n)+ indicates that direct photo-induced fragmentation processes are more important at short times than the statistical unimolecular decay.