A kinetic model of the sustained discharge HgBr laser

A kinetic model of the sustained discharge Ar/HgBr2 laser is developed from an experimental base. The choice of Ar as the buffer gas is supported by measurements of the specific fluorescence and laser efficiency in the buffer mixtures (Ar, Ar+5% Xe, Ne+10% Xe, Ne+10% N2). A computational treatment of the coupled photon and kinetic equations is described. Gain measurements determine a peak HgBr (B-X) stimulated emission cross section of 1.6×10−16 cm2±20% at 502 nm. Absorption measurements between 515 and 530 nm show the presence of a large, broad band absorption tentatively assigned to HgBr+2 with a cross section of 2×10−18 cm2. An upper bound of 5×10−9 cm3 sec−1 is placed on the rate constant for electron collisional quenching of the HgBr(B) state. The laser extraction efficiency of 65% is modeled by a lower level collisional deactivation by Ar with a rate constant 6.0×10−12 cm3 sec−1. Discharge impedance is measured as a function of E/N and the ionizing electron beam current density. Using the new data a good description of laser efficiency is demonstrated if the ratio of HgBr(B-X) fluorescence power to discharge input electical power is set to 6.1%, for 0.8% HgBr2 in Ar at E/N=8×10−17 V cm2.