Population distribution of atomic uranium in the afterglow of a pulsed hollow-cathode discharge

Abstract

From laser absorption measurements we have deduced the time evolution of the population distribution of atomic uranium in the afterglow of a pulsed hollow-cathode type discharge. The vapour generator operates with xenon as the discharge sustaining gas at a pressure of 280 Pa (2.1 Torr). The current pulse characteristics are width 250 µs and height 1.5 A. The pulse repetition frequency is 100 Hz. It is shown that the populations in the three metastable levels at 6249, 3868 and 3800 cm^–1 decrease almost exponentially in a time interval between 150 and 300 µs. From 400 µs onwards in the afterglow, the atom population is essentially shared between the ground and the first metastable (620 cm^–1) levels. Furthermore, starting from 9 ms in the afterglow more than 80% of the U atoms are found in the ground level.