2s-Excitation and Photoionization of Neon Clusters

Abstract

Variable size neon clusters consisting mostly of surface sites are investigated in the Ne 2s regime (44–50 eV), which is characterized by Rydberg-/exciton-transitions. Distinct changes in peak shape are observed upon the transition from the atom to clusters as probed by yields of mass selected cations and threshold photoelectron spectra, where changes in coupling to the underlying 2p continuum are observed in clusters. Cluster size dependent changes in cation yields are observed and rationalized in terms of a plausible autoionization mechanism, which involves 2s ionization and is followed by charge delocalization via Interatomic Coulombic Decay (ICD). Size- and site-dependent changes in energy position of the Rydberg states as well as 2s ionization energy are also observed. These results are interpreted along with model calculations which allow us to assign the experimental results in greater detail. The experimental and theoretical results are also used to deduce the exchange interaction of the Rydberg electron with the surrounding atoms and the induced polarization of the surrounding atoms in small neon clusters.