Accuracy of stark broadening calculations for ionic emitters

The standard static-ion impact electron theory of line broadening is assessed with a calculation of the He II P-alpha line over a broad range of plasma conditions. Ion dynamics, an improved electron collision operator, and accurate atomic physics are included in the computation. Simulations also have been performed to validate effects included in the calculation at higher densities. Calculated linewidths are compared with experiment over more than two decades in electron density, and broad agreement is found. This provides the first critical evaluation of the assumptions of Stark broadening theory. The profiles also display the first unambiguous evidence of ion dynamics.