The 2p core-level electron binding energies of size-selected silicon cluster
ions have been determined from soft x-ray photoionization efficiency curves.
Local chemical shifts and global charging energy contributions to the 2p
binding energy can be separated, because core-level and valence-band electron
binding energies exhibit the same inverse radius dependence. The experimental
2p binding energy distributions show characteristic size-specific patterns
that are well reproduced by the corresponding electronic density of states
obtained from density functional theory modeling. These results demonstrate
that 2p binding energies in silicon clusters are dominated by initial state
effects, i.e., by the interaction with the local valence electron density, and
can thus be used to corroborate structural assignments
