Population inversions in C iv in a recombing theta-pinch plasma

Population inversions on the 5g–4f and 4f–3d transitions of C iv at 253.0 and 116.9 nm have been observed in the recombination phase of a theta-pinch plasma initially containing 14 mTorr of acetylene and 0.5 mTorr of hydrogen gas. Population ratios of 17:11:1 for the 5g, 4f, and 3d levels were deduced from measured absolute line intensities of the 5g–4f and 4f–3d, and 3d–2p transitions at 253.0, 116.9, and 38.4 nm. The resulting gain–length product for a single pass through the 23-cm-long plasma column, based on the measured Doppler-broadened linewidth, is 2.3% at 116.9 nm and 5.8% at 253.0 nm.