Extreme-ultraviolet spectroscopy of highly charged xenon ions created using an electron-beam ion trap

Abstract

Extreme-ultraviolet spectra of xenon ions have been recorded in the 4.5 to $20\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ wavelength region using an electron beam ion trap and a flat field spectrometer. The electron beam energy was varied from $180\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ to $8\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and radiation from charge states ${\mathrm{Xe}}^{6+}$ to ${\mathrm{Xe}}^{43+}$ 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 ${\mathrm{Xe}}^{35+}$ through to ${\mathrm{Xe}}^{41+}$ with estimated wavelength uncertainties of $\ifmmode\pm\else\textpm\fi{}0.003\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. 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 ${\mathrm{Xe}}^{42+}$ and ${\mathrm{Xe}}^{43+}$ revealed enhancement of the total ionization cross sections, due to excitation-autoionization of $n=2$ electrons to $n=3$ levels, in the ${\mathrm{Xe}}^{41+}$ and ${\mathrm{Xe}}^{42+}$ charge states.