Exponential photoelectron spectra in Na clusters

Abstract

We discuss photoelectron spectra (PES) of sodium clusters at moderate and high intensities. At the lower end of the intensity regime the PES still show their characteristic structure reflecting the single-electron states of the cluster. At larger intensities, the PES become smooth showing a simple exponential decrease. We work out that this exponential trend can be explained in terms of multi-photon emission and is thus not necessarily a sign of thermalization.