Low pressure DBD in He–Ne mixture. Spectroscopy of the afterglow

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 $2p^55s$ configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. It is shown that in the early stage of the DBD afterglow, the distribution of the populations over the $2p^55s$ and $2p^54d$ levels of the neon atom is due to the excitation transfer mechanism Не$(2^1S_0)$ + Ne $\to$ He$(1^1S_0)$ + Ne$^*$. In the late afterglow with the departure of helium atoms Не$(2^1S_0)$, emission in the visible region of the spectrum is formed mainly by transitions from levels of the $2p^53p$ configuration, the population of which is associated with Не$(2^3S_1)$ atoms. At this stage, the population of the $2p^55s$ and $2p^54d$ 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.