Population inversion of Cd+excited states in the plasma of cadmium vapor vacuum arc

Population densities of excited states in a cadmium vacuum arc plasma were investigated spectroscopically and their absolute values were calculated using absolute measurements of the spectral lines' intensity emitted from the plasma. A transient population inversion was observed among the
ng^{2}G(n = 6-11)
group of levels and between the upper and lower levels of the transitions:
6g^{2}G_{9/2} \rightarrow 4f^{2}F_{7/2}, 10g^{2}G_{9/2} \rightarrow 4f^{2}F_{7/2}, 11g^{2}G \rightarrow 4f^{2}F_{7/2}
, whose maximal estimated one-pass gain values are 1.75, 1.002, and 1.004, respectively.