Estimate of the rate of collisional-radiative recombination of doubly charged Ne$^{++}$ ions from the results of a spectroscopic experiment

An experiment was set up to study the afterglow of an extended barrier discharge in low-pressure neon containing Ne$^+$, Ne$^{2+}$, and Ne$^{++}$ ions by kinetic spectroscopy. Observation conditions: neon pressure $\sim$0.8–1.7 Torr, electron density in the afterglow stage $[e]\sim$10$^{11}$ cm$^{-3}$. In order to compare the rates of collisional-radiative recombination of Ne$^+$ and Ne$^{++}$ ions, the effect of pulsed “heating” of decaying plasma electrons by a weak high-frequency field on the intensities of atomic and ion lines was observed. The presented data show that in such a plasma, short-term suppression of recombination processes by electron heating leads to an increase in the brightness of spectral lines in the atomic and ion afterglow spectra, and the reaction of the lines of the latter turns out to be much stronger. Based on simple estimates, it is shown that this effect is due to the difference in the recombination rates of the Ne$^+$ and Ne$^{++}$ ions, and this difference turns out to be beyond the scope of theoretical concepts.