Spectroscopic study of an electrode microwave discharge in argon and argon–hydrogen mixtures

Abstract

The results of an optical emission spectroscopy study of low-pressure microwave induced discharge in argon, argon–hydrogen (0.9% H 2) and hydrogen–argon (5% Ar) mixture are reported. At four different pressures the Boltzman plot of relative ArI line intensities is used to measure electron excitation temperature, which was close to 3000 K in argon and in argon–hydrogen mixture discharges. The spatial distributions of light emission from argon and hydrogen–argon discharges are recorded with CCD camera and compared with spectroscopically observed spatial distributions of the ArI 415.8 nm line intensity in argon and the H β line intensity in hydrogen–argon mixture at three different pressures. The variation of light intensity with pressure for argon lines ArI 842.5 nm, ArI 750.3 nm and ArI 419.8 nm as well as for hydrogen H β line is also studied. For high- and low-lying energy levels in argon and in argon–hydrogen mixture, a different dependence of spectral line intensity upon gas pressure is detected. In hydrogen–argon mixture, a non-linear decrease of argon and hydrogen spectral line intensity with an increase of gas pressure is observed.