Dissociative Recombination of K₂⁺ and Rb₂⁺ in Diode-Pumped Alkali Lasers: Potential Energy Curves and Atomic Products

Dissociative recombination (DR) of K₂⁺ and Rb₂⁺ ions is one of the most important processes in K and Rb diode-pumped alkali lasers (DPALs) strongly affecting their power. We report on the calculations of potential energy curves of the K₂⁺ and Rb₂⁺ molecular ions and of the diabatic ¹Σ⁺, ³Σ⁺, ¹Δ, ³Δ, ¹Π, ³Π, ¹Φ, and ³Φ valence states of K₂ and Rb₂ that provide the routes for DR of the ions. These curves are required for subsequent calculations of DR rate constants. It was found that the most likely DR routes for K are along the dissociative states 6¹Σ_g⁺, 5³Σ_u⁺, and 2³Δ_u and for Rb only 6¹Σ_g⁺. The excited states of K atoms produced by DR are 4²P and 5²P. Most of the Rb atoms produced by DR are in the 6²P excited state, while a small fraction of the atoms produced by the less likely routes along two states of Rb₂ are in the 5²P state. This conclusion contradicts the kinetic scheme for K and Rb DPAL proposed elsewhere, and thus the kinetic schemes of these DPALs should be modified according to the present results.