Real-time observation of ultrafast ionization and fragmentation of mercury clusters

We report on time-resolved multiphoton ionization and fragmentation dynamics of free Hg-n-clusters (n less than or equal to 110) with femtosecond laser pulses. Already at laser intensities of 10(11)W/cm(2) we observe prompt formation of singly, doubly, and triply charged Hg, clusters. In pump-probe experiments short-time (0-5 ps) oscillatory modulations of the transient Hg-n(+) and Hg-n(2+) signals are observed which indicate an intermediate state dynamics common to all observed cluster sizes and charge states. Long-time (0-200 ps) transient ionization signals show caged dissociation and recombination chromophore dynamics.