Stability criteria in metal vapor discharges

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.