Simulation microfield method for plasma spectroscopy

Abstract

A computer simulation method has been developed to analyze the effect of the ionic microfield fluctuations on the spectral line shape of hydrogenic emitters. The simple simulation model involves use of independent perturbers interacting with the emitter through a Debye potential and is valid for weakly-coupled plasmas. The dipole autocorrelation function of the emitters are obtained by numerical integration of the Schrödinger equation for the time- evolution operator. For a large domain of plasma parameters, our calculations demonstrate that the ion-broadening mechanism belongs to a regime which is intermediate between the limiting impact and quasistatic approximations. The effect of ion-microfield fluctuations on the redistribution function has also been analyzed. This function enters into radiative transfer calculations and is often approximated by complete redistribution, which assumes that the emission profile is the same as the fluorescence profile. For highly charged emitters, this approximation is no longer valid and we have partial redistribution conditions. The occurrence of partial redistribution depends critically upon competition of the rates of spontaneous emission, Stark shifts, electron broadening, and the rate associated with ion-microfield fluctuations. By using the simulation model for an estimate of the latter rate, it is possible to analyze the role of ion-microfield fluctuations in partial redistributions.