Observation of intense soft-x-ray lasing at the J = 0 to J = 1 transition in neonlike zinc

We present experimental results from recent studies of soft-x-ray lasing in Ne-like Zn (Z = 30). The lasing plasma was produced by irradiation of slab targets as much as 2 cm long with intensities of -1.4 X 10¹³ W cm ² at A = 1.06, um in pulses of 600 ps (FWHM). Amplification at three 3p-3s transitions was observed. While the J = 2 to J = 1 transitions at 262 and 267 A provided gain coefficients of 2.3 and 2.6 cm¹, respectively, the J = 0 to J = 1 transition at 212 A exhibited a significantly larger gain of 4.9 cm¹ and yielded a much brighter signal. Furthermore, its temporal characteristics were revealed to be unlike those of the J = 2 to J = 1 transitions. The results indicate that the J = 0 to J = 1 line originates from a different plasma region than do the J = 2 to J = 1 lines and that the temporal evolution of the pumping process into its upper lasing level J = 0 differs considerably from that to the J = 2 levels. In addition, the gain and the gain-length product of -10 achieved in this experiment are, to our knowledge, the highest ever reported for a driving laser of similar energy (-450 J).