Electron-collisional excited-state kinetics in argon and mercury electrical discharges

Abstract

The effects of inelastic electron‐collisional processes on the efficiency for population of electronic states in atomic argon and mercury in an electrical discharge have been studied theoretically as a function of excited‐state population fraction. Electron impact excitation rates for the lowest‐lying electronic states and rates for ionization from these states have been determined through the use of the Boltzmann transport equation for the range 5×10⁻¹⁷?E/N?10⁻¹⁵ V cm². It was found that the electron distribution functions are highly non‐Maxwellian. Also, the electron excitation rates from the ground state, and consequently the efficiency for populating these states by electron impact, can be reduced significantly as the excited‐state population fraction X* is increased; in Ar this occurs for X*≳10⁻⁵. These effects impose fundamental limitations on the efficiency and power extraction that can be obtained from electrical‐discharage‐excited visible and uv lasers that use electronic states in the noble gases for pumping the lasing species.