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 ionizatio n and fragmentation has been studied in beam experiments applying femt osecond pump-probe techniques in combination with ion and electron spe ctroscopy. Three dimensional wave packet motions in the trimer Na3 gro und state X and excited state B have been observed. We report the firs t study of cluster properties (energy, bandwidth and lifetime of inter mediate resonances Na(n)) with femtosecond laser pulses. The observat ion of four absorption resonances for the cluster Na8 with different e nergy widths and different decay patterns is more difficult to interpr et 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.