Surface explosion and subsequent core expansion of laser-heated clusters probed by time-resolved photoelectron spectroscopy

Abstract

The dynamics of nanoplasma produced by an intense near-infrared pulse was investigated by time-resolved soft x-ray photoelectron spectroscopy. The pump-probe electron spectra indicate transient evolution of the electronic states of the constituent atoms and ions during plasma formation and disintegration. The delay dependence of photoelectron yields supports two-step fragmentation of laser-heated clusters, i.e., rapid explosion of surface ions followed by slow expansion of neutral atoms. The speed of the neutral core expansion was evaluated by comparing the experimental data with a model of uniform neutral core expansion.