Recombination and Ion-Conversion Processes in Helium-Neon Mixtures

Detailed studies of the time dependence of the spectral emission and that of the number density of ions have been made during the decay period of plasmas produced in helium containing various concentrations of neon atoms. The occurrence of the recombination of ${\mathrm{Ne}}^{+}$ via the collisional recombination process with a recombination coefficient proportional to the electron density is established for the first time. The studies confirm the occurrence of recombination processes previously reported for $\mathrm{He}_2^{}{}_{}{}^{+}$ and $\mathrm{Ne}_2^{}{}_{}{}^{+}$. Evidence has also been found for the population of the $4d$ levels of neon by $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)$ metastable atoms. New values for the rate constants of the following processes were obtained: ${\mathrm{Ne}}^{+}+2\mathrm{}\mathrm{He}\to {\left(\mathrm{HeNe}\right)}^{+}+\mathrm{He}$ (2.1 × ${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^6$ ${\sec }^{-1\mathrm{}}$); ${\mathrm{Ne}}^{+}+\mathrm{Ne}+\mathrm{He}\to {\left(\mathrm{HeNe}\right)}^{+}+\mathrm{Ne} \mathrm{and} \to {{\mathrm{Ne}}_2}^{+}+\mathrm{He}$ (3.0 × ${10}^{-31\mathrm{}}$ ${\mathrm{cm}}^6$ ${\sec }^{-1\mathrm{}}$); ${\left(\mathrm{HeNe}\right)}^{+}+\mathrm{Ne}\to {{\mathrm{Ne}}_2}^{+}+\mathrm{He}$ (3 × ${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$) — all at a gas temperature of 300 °K.