Diagnostics of capillary mercury-argon high-frequency electrodeless discharge using line shapes

The profiles of the 253.7 nm spectral line, emitted from the capillary argon-mercury isotope high-frequency electrodeless discharge, are measured by means of a pressure-scanned Fabry-Perot spectrometer. Spectral line profiles are collected from two lamps at the argon pressure of 2 and 10 Torr, in dependence on the discharge current and Hg vapor densities corresponding to the cold spot temperatures of 25-80 °C. By means of a multi-parameter non-linear line profile fitting procedure of multiple overlapping self-reversed Voigt profiles, the temperature of the radiating atoms and the optical density were estimated. The capillary and spherical discharge conditions were compared. The optimal working conditions avoiding self-absorption were obtained. The measurements were completed by means of the Zeeman scanning spectrometer, allowing the getting of additional information about the instrument functions. The necessity to take into account the instrument function also by comparable small values of its width was shown.