The puzzling optical-absorption and photoelectron spectra of neutral and anionic Ag clusters.

The optical absorption and photoelectron spectra (PES) of neutral and anionic Ag clusters have been studied using the particle-swarm optimization technique and time-dependent density functional theory. The results demonstrate that the enigmatic optical-absorption spectrum of neutral Ag cluster is derived from the ground state structure with T symmetry rather than the almost degenerate isomer with D symmetry. The transitions at 3.57-3.65 eV should be ascribed to the neutral fragment cluster Ag. Meantime, the optical-absorption and PES of neutral and anionic Ag cluster are for the first time given a reasonable unified explanation.