On the Selectivity of Population of the Neon Excited Levels in the Decaying He–Ne Plasma

The results of a spectroscopic study of the afterglow of a pulsed discharge in a He–Ne mixture are presented, showing the unique selective population of the upper level of the 2p⁵4p configuration (3p₁ in Paschen's notation) of a neon atom at a helium pressure of tens of Torr. The main measurements were conducted under conditions of competition between the excitation transfer from metastable He atoms (2¹S₀) and the dissociative recombination of HeNe⁺ ions with electrons as sources of excited atoms. Helium pressure P_He ≈ 0.08–20 Torr, neon P_Ne ≈ 0.0005–0.003 Torr, the electron density [e] < 10¹¹ cm^–3. The results of the experiment indicate the existence of a mechanism that forms with an increase of helium pressure such a distribution of populations over 2p⁵4p levels, in which more than 60% of the radiation flux of 2p⁵3s ← 2p⁵4p transitions is concentrated in one spectral line of 352.0 nm.