Stability criteria in metal vapor discharges

Abstract

In this letter we discuss the stability criteria in recombination‐ and attachment‐dominated metal vapor laser discharges. The mercury halide laser discharges are typical of attachment‐dominated discharges, while the metal vapor exciplex lasers, like CdHg*, are typical of recombination‐dominated discharges. In high‐power electronic transition laser discharges, a relatively large excited‐state population exists which dominates the stability of these discharges. This occurs because the excited states have a smaller ionization potential and larger ionization cross section than the ground state. As a result, multistep ionization is the dominant ionization. When three‐step ionization is dominant and electron mixing of the excited states is unimportant, attachment‐dominated discharges will be stable if the attachment rate β⩾mν_i0, where 2<m⩾3 and ν_i0, is the equilibrium ionization rate. For a recombination‐dominated discharge the criterion in this limit is an_e0⩾mν_i0 where 1.0<m⩾1.5 and a is the recombination coefficient and n_e0 is the equilibrium electron density.