FRAGMENTATION PROBABILITIES OF EXCITED ALKALI CLUSTERS

Employing transient resonant two-color two-photon ionization spectrosc opy in the picosecond and femtosecond regime, we have investigated the fragmentation dynamics of several excited electronic states of alkali clusters. In the case of the Na-3 C-state a simple energy-level model well describes the single exponential decay found for the temporal ev olution of the transient spectra. This allowed to estimate fragmentati on probabilities of the C-state vibrational bands as well as the onset of predissociation. For larger clusters, Na-n as well as K-n with n g reater than or equal to 3, the ultrafast transients could be measured. By means of an improved fragmentation model the fragmentation probabi lities are determined as a function of the cluster size. Significant d ifferences between Na-n and K-n clusters are discussed.