Direct Observation Of Interatomic Coulombic Decay And Subsequent Ion-Atom Scattering In Helium Nanodroplets

We report on the experimental observation of interatomic Coulombic decay (ICD) in pure He-4 nanoclusters of mean sizes between N similar to 5000 and 30 000 and the subsequent scattering of energetic He+ fragments inside the neutral cluster by using cold target recoil ion momentum spectroscopy. ICD is induced in He clusters by using vacuum ultraviolet light of h nu = 67 eV from the BESSY II synchrotron. The electronic decay creates two neighboring ions in the cluster at a well-defined distance. The measured fragment energies and angular correlations show that a main energy loss mechanism of these ions inside the cluster is a single hard binary collision with one atom of the cluster.