High-resolution measurements of Mg xi and Cu xx resonance and satellite transitions and the resonance defect in the Mg-pumped Cu x-ray laser scheme

Abstract

Magnesium and copper plasmas produced by 2-ns pulses of a Nd-glass laser were used to investigate satellite spectra of Li-like Mg x and Na-like Cu xix and to verify a near resonance between Mg xi and Cu xx transitions, which is the basis of a proposed resonantly photopumped x-ray laser scheme. The emission was measured with a spherical crystal spectrograph that provided high spectral resolution (\ensuremath{\lambda}/\ensuremath{\Delta}\ensuremath{\lambda}\ensuremath{\approxeq}8000) and spatial resolution in one dimension. The high resolution allowed improved wavelength measurements for a number of n=2\ensuremath{\rightarrow}1 Mg x transitions that are satellites to the He-like resonance line, including transitions with n=3,4 spectator electrons. Using composite targets, the spatial resolution of the spectrograph enabled highly accurate measurements of 2p-4d Na-like copper transitions. Collisional-radiative models were used to assist the identification of the Mg x and Cu xix transitions. Finally, the wavelength difference between the 2${\mathit{p}}^{6}$-(2${\mathit{p}}^{5}$${)}_{3/2}$4${\mathit{d}}_{5/2}$(J=1) Cu xx transition and the 1${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$--1s2${\mathit{p}}^{3}$${\mathit{P}}_{1}$ Mg xi intercombination line was measured to be 2.5\ifmmode\pm\else\textpm\fi{}0.8 m\AA{}, with the copper line having a longer wavelength.