Relativistic many-body calculations of energies of $n=3\mathrm{}$ states in aluminumlike ions

Energies of ${3l3l}^{\prime }{3l}^{″}$ states of aluminumlike ions with $Z=14\mathrm{}–100$ are evaluated to second order in relativistic many-body perturbation theory starting from a ${1s}^2{2s}^2{2p}^6$ Dirac-Fock potential. Intrinsic three-particle contributions to the energy are included in the present calculation and found to contribute about 10–20 % of the total second-order energy. Corrections for the frequency-dependent Breit interaction and the Lamb shift are included in lowest order. A detailed discussion of contributions to the energy levels is given for aluminumlike germanium $\mathrm{}(Z=32\mathrm{}).$ Comparisons are made with available experimental data. We obtain excellent agreement for term splitting, even for low-Z ions. These calculations are presented as a theoretical benchmark for comparison with experiment and theory.