Collective excitations in silver cluster anions and kations

Abstract

Pos. and neg. Ag cluster ions are produced by sputtering of solid Ag by 25 keV Xe+ bombardment. After mass selection, collinear ion beam depletion was used to measure abs. photofragmentation cross-sections in the photon energy range from .plcnst..omega. = 2.0-5.7 eV. Giant resonances were found which can be interpreted in terms of a collective electron oscillation. For spherical clusters (e.g., Ag19-, Ag21+) single resonances dominate the spectra, whereas deformation (e.g., Ag9-, Ag11+) induces a splitting into 2 components.