Non-Maxwellian electron-energy distribution from cluster nanoplasmas

Abstract

Studies on ionization and electron emission from cluster nanoplasmas in intense laser fields are largely limited to experiments on single isolated clusters. We measure electron emission from ionization of clusters at higher cluster ensemble densities and find that the electron-energy spectra is highly non-Maxwellian. A comprehensive model is developed to account for the change in electron-energy spectrum and the depletion of the low-energy electron yield. It is shown that elastic and inelastic collisions account for the observed non-Maxwellian spectral shape and the computed spectrum compares well with the measurements. Furthermore, it is deciphered that the electrons that stream out of the focal volume, collisionally ionize every atom in the clusters at the periphery (< 100 μm) of laser focus.