Stark Broadening of Isolated Spectral Lines from Heavy Elements in a Plasma

Abstract

The frequency distributions of neutral cesium and argon lines broadened by local fields of both electrons and ions in a plasma are calculated in the classical path approximation. The electron collisions are treated by an impact theory originally developed for neutral helium lines which takes into account deviations from adiabaticity. For the ion effects the adiabatic and in most instances also the quasi-static approximation can be used, if necessary corrected for ion-ion correlations and Debye shielding. Atomic matrix elements are obtained with the Bates and Damgaard method and are checked against measured Stark coefficients. Stark broadening parameters are tabulated for the argon lines arising from $2p$ and $3p$ levels (Paschen's notation) and for the cesium lines in the series $6S\ensuremath{-}nP$, $6P\ensuremath{-}nD$ with $n$ up to 20, $6P\ensuremath{-}nS$ with $n$ up to 15, and $5D\ensuremath{-}nF$ with $n$ up to 10. Approximate formulas for total widths and shifts are suggested. For the widths, an accuracy of 20% is indicated by the good agreement with experiments. Measured shifts are only available for argon. Here the calculated shifts tend to be 20% larger than the measured values.