Radiative recombination and photoionization cross sections for heavy element impurities in plasmas

Full text: We have performed fully relativistic calculations of total cross sections for the radiative recombination of heavy element impurities with electrons, and subshell photoionization cross sections for 31 ions of Fe, Ni, Cu, Mo and W, as important elements in plasma studies. The electron wave functions were determined by means of the Dirac-Fock method, with exact consideration of the exchange interaction between electrons. Adequacy of the model and accuracy of the calculations were analyzed and assessed. Electron kinetic energy range is 4 eV to 50 keV. The total radiative recombination cross section was obtained by calculation of the subshell cross sections for ground and all excited electron states up to states with principal quantum number n = 20. Subshell photoionization cross sections for excited states with ≤ 12 and orbital momenta l ≤ 6 were fitted by a simple analytical expression with five fitting parameters. Fits were produced in the photon energy range from 4 eV above the ionization threshold Eth to the kmax energy where the photoionization cross section falls by five orders of magnitude as compared with the maximum value. Usually, kmax ≤ 100Eth for the s, p, d and f shells, and kmax ≤ 10Eth for the g, h and i shells. As a rule, fitting was carried out with good accuracy when the relative root-mean-square uncertainty was ≤ 2%. The total radiative recombination cross sections and the fit parameters for the subshell photoionization cross sections were presented in tabular form. (author)