Dissociation Energy and Dissociative Recombination of $${\text{Ne}}_{2}^{ + }$$ and HeNe+ Ions

Abstract

We present the results of our study of a weakly ionized decaying helium plasma with a small admixture of neon by means of kinetic spectroscopy. The experimental conditions are a helium pressure of 10–38 Torr, an electron density [e] ≤ 2 × 1011 cm–3, and a neon density [Ne] ≤ 2 × 10–4 [He]. The recombination processes of $${\text{Ne}}_{2}^{ + }$$ , $${\text{He}}_{2}^{ + }$$ , HeNe+, and Ne+ ions with electrons have been identified by the decaying-plasma radiation. The neon afterglow spectrum at [e] ≤ 1011 cm–3 is shown to be formed mainly by dissociative recombination of $${\text{Ne}}_{2}^{ + }$$ and HeNe+ ions in the ground vibrational state $${v}$$ = 0. The early afterglow of a number of atomic neon lines is formed by the well-known process of excitation transfer from helium atoms in metastable states He(23S1, 21S0). At [e] > 1011 cm–3, the afterglow spectrum is enriched due to the collisional-radiation recombination of Ne+ ions. In the recombination stage of the afterglow at room electron temperature, the existence of a clear upper bound on the excitation energy of the atomic neon levels being populated is characteristic of the dissociative recombination of both molecular ions. For $${\text{Ne}}_{2}^{ + }$$ this is the 3p1 level (in Paschen notation) with an energy of 20.369 eV, with the levels closest to $${\text{Ne}}_{2}^{ + }$$ ( $${v}$$ = 0) in energy being 3p3 and 3p2 with energies of 20.26 and 20.3 eV, respectively; for HeNe+, this is the 5 $$d_{1}^{'}$$ level with an energy of about 21.02 eV. These values are proposed to be taken as the energies of $${\text{Ne}}_{2}^{ + }$$ and HeNe+ ions in the ground vibrational state.