Stark broadening of the 1640- and 4686-Å lines of ionized helium

Abstract

The Stark-broadened profiles of the 1640- and 4686-\AA{} lines of ionized helium have been calculated using an approximation to the electron broadening operator in the unified classical-path theory of Smith, Vidal, and Cooper. The approximation is such that the results reproduce the time-ordered impact-theory results in the line center, and the ionized-radiator quasistatic results in the far wings. Sample calculations at ${n}_{e}={10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and $T=40000$ \ifmmode^\circ\else\textdegree\fi{}K are found to give significantly more narrow profiles than the corresponding modified-impact-theory results because of a different treatment of the lower-state interaction. Indirect comparison with experiment indicates that the calculated lines are too narrow, but it is expected that the inclusion of neglected effects of ion dynamics and inelastic collisions would improve agreement.