Relativistic multireference many-body perturbation theory is generalized to calculate the energies of highly excited levels in multivalence-electron ions of iron group elements responsible for soft-x-ray emission lines. Term energies of the highly excited $n=4$ states arising from the $3s^{2}3p4l\left(l=0–3\right)$ and $3s3p^{2}4l\left(\mathrm{l}=0–3\right)$ configurations in $\mathrm{Fe}\text{XIII}$ are computed to high accuracy. Theoretical electric dipole transition probabilities and wavelengths of the transitions to low-lying $n=3$ levels are compared with solar and laboratory lines to identify hitherto unidentified $\text{and}∕\text{or}$ poorly characterized extreme ultraviolet and soft-x-ray spectral lines. $E1$, $E2$, and $M1$ decay rates and lifetimes of lower excited levels of the $n=3$ manifold are evaluated as a benchmark for future experiments.

• Received 9 January 2004

DOI:https://doi.org/10.1103/PhysRevA.69.062503