Extreme-ultraviolet spectra of xenon ions have been recorded in the 4.5 to 20 nm wavelength region using an electron beam ion trap and a flat field spectrometer. The electron beam energy was varied from 180 eV to 8 keV and radiation from charge states Xe 6+ to Xe 43+ was observed. Our measured wavelengths were compared to atomic structure calculations using the Cowan suite of codes. We have measured seventeen previously unreported features corresponding to transitions in Xe 35+ through to Xe 41+ with estimated wavelength uncertainties of ±0.003 nm. It was found that for the case of continuous injection of neutral xenon gas a wide range of charge states were always present in the trap but this charge state distribution was greatly narrowed, towards higher charge states, if a sufficiently low gas injection pressure was employed. The energy dependence of spectral lines arising from Xe 42+ and Xe 43+ revealed enhancement of the total ionization cross sections, due to excitation-autoionization of n = 2 electrons to n = 3 levels, in the Xe 41+ and Xe 42+ charge states.
Theoretical EUV emission spectra of gadolinium and terbium ions calculated with the Cowan suite of codes and the FAC relativistic code are presented. 4d−4f and 4p−4d transitions give rise to unresolved transition arrays in a range of ions. The effects of configuration interaction are investigated for transitions between singly excited configurations. Optimization of emission at 6.775 nm and 6.515 nm is achieved for Gd and Tb ions respectively by consideration of plasma effects. The resulting synthetic spectra are compared with experimental spectra recorded using the laser produced plasma technique.
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