The 2$p$ 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 2$p$ binding energy can be separated, because core-level and valence-band electron binding energies exhibit the same inverse radius dependence. The experimental 2$p$ 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 2$p$ 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.

• Received 23 March 2012

DOI:https://doi.org/10.1103/PhysRevB.85.195454