Stark broadening of the hydrogen H γ spectral line at moderately low plasma electron densities

Abstract

The usage of the hydrogen H γ spectral line for plasma diagnostics, based on Stark broadening at moderately low electron densities (of the order of 10 15 cm −3), is experimentally tested and analyzed. As a plasma source, a low-pressure pulsed arc operating in a He–H gas mixture was used. In this electron density range, the Stark broadening of low-order Balmer lines is small, but the broadening of the higher-order members is considerable. Plasma electron densities were deduced from the halfwidth (FWHM) of the measured H γ profiles in conjunction with the available theoretical results. Further comparison among the electron density values obtained independently using a laser interferometry method and the shape of the He I 4471 Å spectral line was also performed. Upon authors knowledge this is the first study of H γ spectral line undertaken in this way.