Diagrammatic many-body perturbation theory applied to highly ionized atoms of the copper isoelectronic sequence

Many-body diagrammatic perturbation theory has been applied to the calculation of ionization energies and multiplet strengths for two highly ionized atoms of the copper isoelectronic sequence. A unified Hartree-Fock zeroth-order Hamiltonian the eigenfunctions of which include both open- and closed-shell orbitals has been constructed for systems with a single open shell. Correlation energies for the excited $4p$ states as well as the ground $4s$ states of Kr VIII and Mo XIV were computed by means of individual basis sets generated for each state. The distribution of the 3l-4l^' correlation energy among second- and higher-order terms differed significantly for the two ions. In Mo XIV, most of the correlation energy was concentrated in second-order, with small third-order effects. In Kr VIII, however, second-order results were substantially changed by higher-order diagrams, particularly in the case of the $4p$ state. Correlated multiplet strengths for the 4s²S-4p²P resonance transition were computed, including first-order corrections to the Hartree-Fock zeroth-order wave functions for both initial and final states. The results of these calculations are in excellent agreement with those of recent multiconfiguration Hartree-Fock calculations.