Accurate wavelength determination of the lasing and nonlasing lines in laser-produced germanium plasma

The XUV spectra from laser-produced germanium plasma are investigated. The energy levels of the 2s(2)2p(5)3l and 2s2p(6)3l states with l = 0, 1, 2 and the oscillator strengths for the transitions between these levels are calculated by the relativistic configuration-interaction (RCI) method. A high-resolution (lambda/Delta lambda similar to - 16 000) grazing-incidence spectrometer is used to measure the spectra in 185-300 Angstrom. The wavelengths of the five lasing lines in Ne-like Ge and the wavelengths of the nonlasing lines have been determined with +/- 0.04 Angstrom accuracy. The observed lines are assigned to the 3-3 transitions in Ne-like and Na-like Ge ions. The energies of the excited states in Ne-like Ge ions derived from the spectroscopic measurements are compared with the RCI and other theoretical calculations.