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

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 ({λ}/{Δ}{λ}{}8000) and spatial resolution in one dimension. The high resolution allowed improved wavelength measurements for a number of n=2{→}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 2p⁶-(2p⁵{)}3/2$4${d}5/2$(J=1) Cu xx transition and the 1${s}²¹{S}₀$--1s2${p}³P₁ Mg xi intercombination line was measured to be 2.5±{}0.8 m{}, with the copper line having a longer wavelength.