Atomic clusters of various sizes irradiated with short intense pulses of VUV radiation

TL;DR

This paper models the ionization dynamics of atomic xenon clusters exposed to intense VUV pulses, revealing size-dependent effects and aligning well with experimental data.

Contribution

It provides a detailed kinetic Boltzmann model for cluster ionization, highlighting size effects and matching experimental observations.

Findings

Ion charge states increase with cluster size.

Energy absorption per atom varies with cluster size.

Charge distribution depends on cluster surface ions.

Abstract

Non-equilibrium processes following the irradiation of atomic clusters with short pulses of vacuum ultraviolet radiation are modelled using kinetic Boltzmann equations. The dependence of the ionization dynamics on the cluster size is investigated. The predictions on: (i) the maximal and average ion charge created, (ii) ion charge state distribution, (iii) average energy absorbed per atom, (iv) spatial charge distribution, and (v) thermalization scales are obtained for spherical xenon clusters containing: 20, 70, 2500 and 90000 atoms. These clusters were exposed to single rectangular pulses of vacuum ultraviolet radiation of various pulse intensities, I ~ 10^{12}-10^{14} W/cm^2 and durations < 50 fs, at a fixed integrated radiation flux of F=0.4 J/cm^2. The results obtained are found to be in good agreement with the available experimental data, especially the dependence on the cluster size, if it is assumed that the ions from the positively charged outer layer of the cluster constitute the dominant contribution to the experimentally measured ion charge state distribution.