Low pressure DBD in He-Ne mixture. Spectroscopy of the Afterglow

Abstract

The paper considers the possibility of using a low-pressure dielectric barrier discharge (DBD) as a plasma source for the active medium of a He-Ne-laser. The results of a spectroscopic study of the decay stage of a DBD plasma of a cylindrical configuration with a pronounced inverse population of the upper level of the 2p55s configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. Based on the analysis of data on the populations of the excited levels of the neon atom and the metastable levels of helium 21S0 and 23S1, it is shown that in the early stage of the DBD afterglow at helium pressures of a fraction of a Torr, the distribution of populations over the 2p55s and 2p54d levels of the neon atom, which is characteristic of the excitation transfer mechanism, is realized. In the late afterglow with the departure of helium atoms He21S0, emission in the visible region of the spectrum is formed mainly by transitions from levels of the 2p53p, configuration, the population of which is associated with He(23S1) atoms. At this stage, the population of the 2p55s and 2p54d states by electron-ion recombination processes is ineffective and does not lead to the formation of population inversion. As an optimal solution in terms of the 632.8 nm line brightness in the afterglow, it is proposed to use a discharge with electrodes along the outer surface of a cylindrical discharge tube, initiated at frequencies that exclude the recombination stage of the afterglow. Keywords: elementary processes, barrier discharge, inverse population, afterglow, helium-neon plasma, excitation transfer