Effects of non-Maxwellian electron distributions on charge-state populations in laser-produced plasmas

Abstract

The effects of a non-Maxwellian electron distribution on the charge-state populations in a plasma with the distribution characterized by the function f(v)=Fm exp[−(v/vm)m] with 2≤m≤5 are investigated. In the underdense region of a laser produced plasma, the parameter m would depend on the electron temperature, electron density, and the average ionization state of the plasma in addition to the optical laser intensity and wavelength. The ion populations are obtained by solving the rate equations in which the coefficients are evaluated by integrating the cross sections over the non-Maxwellian electron distributions. The scaling of m with column density and optical laser intensity in laser exploding foils is obtained. The effects of a non-Maxwellian electron distribution on the charge-state populations in both selenium and molybdenum foils, similar to those used to model recent x-ray laser experiments, are calculated. The effects on the dominant populations are found to be small, less than a dozen of percents.