Soft X-ray lasing in neonlike germanium and copper plasmas

Soft X-ray 3p to 3s lasing in neonlike germanium, Ge(22+), and copper, Cu(19+), in the wavelength interval of 195 to 285 A is observed for the first time, with gain coefficients ranging from 1.7 to 4.1/cm, the higher gain with germanium. The lasing plasmas are produced by the focusing of a driving laser beam (lambda = 1.05 microns, 2-ns FWHM) into an 18-mm-long line onto thin films and slab targets. The measured J = 0 to 1 gain coefficients are comparable to those of the J = 2-1 transitions. The measured wavelengths of the six lasing lines compare favorably with recent calculations. (Author)