Density diagnostic of a uranium laser-produced plasma from the line ratio of Δn=1 transitions in Ni-like uranium

The intensity ratio of the electric quadrupole 3${\mathit{p}}^6$3${\mathit{d}}^{10}$-3${\mathit{p}}_{3/2}^5$4${\mathit{f}}_{7/2}$(J=2) line to the electric dipole 3${\mathit{p}}^6$3${\mathit{d}}^{10}$-3${\mathit{p}}_{1/2}^5$4s line is used as a density diagnostic of a highly ionized uranium laser-produced plasma for electron densities of ${10}^{19}$-${10}^{23}$ ${\mathrm{cm}}^{\mathrm{-}3}$. Calculations show that this ratio is insensitive to the plasma temperature in the range of 1000–4000 eV. Self-absorption of the lines is shown to be unimportant in this density range. Experimental line ratios are compared to the predictions of a Ni-like uranium-ion model that includes 138 excited levels. The densities inferred from this analysis applied to a measured line ratio yield densities of (4.0±0.5)×${10}^{22}$ ${\mathrm{cm}}^{\mathrm{-}3}$. This is in good agreement with models of x-ray production in laser-produced plasmas.