Abstract

The lifetimes of several states in a thallium see-through hollow cathode discharge, or galvatron, are obtained to characterize its potential as an atomic line filter. The lifetimes of the thallium 6<sup>2</sup>D<sub>3/2</sub>, 6<sup>2</sup>D<sub>5/2</sub>, and 7<sup>2</sup>S<sub>1/2</sub> states are measured by time-resolved single-step laser-excited fluorescence by use of a 276.787 nm laser pulse or a 535.046 nm laser pulse and measuring the resulting fluorescence waveform at the appropriate wavelength. Values of 6.4 ± 0.1, 7.5 ± 1.1, and 7.7 ± 0.2 ns were obtained for the 6<sup>2</sup>D<sub>3/2</sub>, 6<sup>2</sup>D<sub>5/2</sub>, and 7<sup>2</sup>S<sub>1/2</sub> states, respectively, which agree with values obtained by previous authors, as well as calculated values. No current dependence was observed for each of these states. The lifetime of the long-lived thallium 6<sup>2</sup>P<sub>3/2</sub>° metastable state was measured by two-step laser-excited fluorescence at various applied currents. The metastable level was pumped by a 276.787 nm laser pulse, and a temporally delayed 535.046 nm laser pulse interrogated the population of the metastable state. Relating the fluorescence intensity to the population of the metastable state as a function of delay time yielded a decay curve for the 6<sup>2</sup>P<sub>3/2</sub>° metastable state. Values of 2.1 ± 0.2, 2.8 ± 0.1, 3.1 ± 0.3, 3.8 ± 0.4, and 4.8 ± 0.6 μs were found for applied currents of 14.0, 12.0, 10.0, 8.0, and 6.0 mA, respectively. The resulting lifetimes for the 6<sup>2</sup>P<sub>3/2</sub>° metastable state clearly show a dependence on the applied current and are expected to be due to collisions with the wall of the cathode, as well as a contribution due to collisions with electrons.

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