Time-resolved laser-induced saturated fluorescence measurements in a thallium see-through hollow cathode discharge: Evaluation of ground state number density and quantum efficiency

A thallium see-through hollow cathode lamp, or galvatron, was studied to evaluate its potential as a narrow band atomic line filter. Time-resolved laser-induced saturated fluorescence was used to evaluate the ground state number density of this glow discharge as a function of current. It was found to produce a sufficient number density at 16.0 mA to absorb 99.9% of incident light from a line source based on an absorption curve-of-growth calculation. A saturation curve was experimentally obtained and modeled with a time-dependent two-level model, as well as a time-dependent three-level model in the presence of a trap. The three-level model showed excellent agreement with the experimental data when a 10 ns pulse duration was used and when collisional rate constants were set to zero. The quantum efficiency of the system was found to be limited only by the spontaneous transition probabilities. Evaluation of these two parameters has shown that a thallium galvatron is an attractive atom reservoir for the applications as a narrow band atomic line filter.