Ionic recoil energies in the Coulomb explosion of metal clusters

The photoionization of metal clusters in intense femtosecond laser fields h as been studied. In contrast to an experiment on atoms, the interaction in this case leads to a very efficient and high charging of the particle where tells of electrons per atom are ejected from the cluster. The recoil energ y distribution of the atomic fragment ions was measured which in the case o f lead clusters exceeds 180 keV. Enhanced charging efficiency which we obse rved earlier for specific pulse conditions is not reflected in the recoil e nergy spectra. Both the average and the maximum energies decrease with incr easing laser pulse width. This is in good agreement with molecular dynamics calculations.