Recombining helium-neon plasma

Recombining helium-neon plasmas are studied theoretically for free electron densities N(e) = 10 to the 13th to 10 to the 17th/cu cm, electron temperatures T(e) = 0.05-0.50 eV, and heavy particle densities less than 10 to the 18th/cu cm. The populations of the helium and neon levels are calculated in the steady sink approximation. It is shown that pure neon plasmas are not well suited as laser media. However, a large stable Ne(4s)-Ne(3p) population inversion can be achieved in a recombining neon-helium plasma. Optimum concentration ratios in the ranges N(Ne)/N(He) not greater than 0.001 and N(Ne)/N(e) = 0.1-0.001 are determined, and simple formulas are derived for the Ne(4s) level populations. Inversion is shown to occur both in a recombining He-Ne plasma and when a recombining pure helium plasma is mixed with neon atoms in the ground state.