Determination of the Electron Density in an Argon Laser Plasma by Spectroscopy of the Hydrogen H_α and H_β Lines

Abstract

From measurements of the H, and H, spectral line profiles in a plasma, a method is developed which allows to separate the contributions of Doppler and Stark broadening. This method is superior to the deconvolution of Voigt profiles, in particular, when the lines are of low intensity. The electron density in the plasma can be calculated from the Stark broadening.An example is the low pressure ( p = 1 hPa) arc discharge of argon ion lasers which is characteristised by electron densities of approximately l O I 4 at heavy particle temperatures of about lo4 K. These plasma parameters lead to a broadening of the Balmer H, and H, spectral lines of hydrogen, which has a low concentration within the discharge area. The spectral lines are broadened due to the electron density dependent Stark eflect and the temperature responsive Doppler effect. The results are consistent with predictions of the argon ion laser modelling.