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 4He nanoclusters of mean sizes between N~5000-30000 and the subsequent scattering of energetic He+ fragments inside the neutral cluster by using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). ICD is induced in He clusters by using VUV 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.