FAST AND ULTRAFAST FRAGMENTATION AND REACTION DYNAMICS IN MOLECULAR CLUSTERS

Two prototype photochemical reactions were studied by femtosecond pump -probe technique: the fragmentation and internal protonation of ammoni a clusters and the energy flow after photoexcitation in the NaNH3 comp lexes. It was found that the (A) over tilde state of clusters (NH3)(n) decays within a few 100 fs and neutral excited (NH3)(n-2)NH4 fragment s are formed. Besides the fragmentation an ultrafast rearrangement wit hin the ammonia cluster (''internal protonation'') is analysed. By com parison of one-and two-colour pump-probe experiments a fast dissociati on of the E-2(4p) state in the NaNH3 complex into Na(3p) + NH3 could b e established.