Ultraviolet photodetachment spectroscopy on jet-cooled metal-cluster anions

Abstract

Metal-cluster anions have been produced by laser vaporization and cooled in a supersonic expansion, without converting neutral clusters into anions via a secondary ionizing agent. After mass-selection, photoelectrons were detached (h= 3.68 eV) from defined anion bunches and analysed in a magnetic bottle-type time-of-flight electron spectrometer. The resulting photoelectron distributions from Al n, Ni n, Ag n and Sn n, n < 22, are compared; all spectra display a dramatic dependence on the cluster size and differ substantially from the respective bulk spectra. The measurements provide information about low-lying excited electronic structures which are missing in the solid metal. Photoelectron thresholds as estimates of electron affinities in part follow a simple electrostatic model.