Wavelengths of 2l→3l′ transitions in L-shell ions of iron and nickel:: A combined configuration interaction and many-body perturbation theory approach

Using a combined configuration interaction and many-body perturbation theory approach, we calculate the level energies of 1s(2)2l(q) and 1s(2)2l(q-1)3l' (1less than or equal toqless than or equal to8) complexes in iron and nickel ions. Comparison of 1s(2)2l(q) energies with experimental results shows that the calculation is accurate to within similar to0.15 eV for these levels. The accuracy of 1s(2)2l(q-1)3l' energies can be slightly worse, at similar to0.5 eV. The theoretical wavelengths of 2-->3 transitions of iron ions are compared with the published experimental measurements, and discrepancies are found to be mostly within +/-10 mAngstrom. Similar accuracy is expected for wavelengths of nickel ions. Such accuracy is a significant improvement over that obtainable with standard configuration interaction methods. A complete table of 2l-->3l' transition wavelengths of all L-shell ions of iron and nickel is presented.