Observation of ion dynamics in the He I 4026A Stark profile

A new experimental method allowing the heavy-particle temperature in an arc plasma to change considerably in otherwise fixed plasma conditions was applied to the study of the Stark broadening of the line He I 4026A and its associated forbidden components at an electron density of nsub(e) = 1015cm-3. Consistent with an earlier experiment, strong deviations from static ion calculations were found. The whole line shape was found to depend sensitively on variations in the heavy-particle temperature and, by including the earlier experiment as well as using the static ion theory, systematic trends could be observed. Though improving some features of the static profile, a recent calculation including ion dynamics still gives poor agreement with experiment. (author)