Relativistic many-body perturbation calculations on extreme ultraviolet and soft-x-ray transition energies in siliconlike iron

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 3s23p4l (l=0-3) and 3s3p24l (l=0-3) configurations in Fe 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 and/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