Accuracy of stark broadening calculations for ionic emitters

The standard static-ion impact electron theory of line broadening is assess ed with a calculation of the He II P-alpha line over a broad range of plasm a conditions. Ion dynamics, an improved electron collision operator, and ac curate atomic physics are included in the computation. Simulations also hav e been performed to validate effects included in the calculation at higher densities. Calculated linewidths are compared with experiment over more tha n two decades in electron density, and broad agreement is found. This provi des the first critical evaluation of the assumptions of Stark broadening th eory. The profiles also display the first unambiguous evidence of ion dynam ics.