RELATIVISTIC MANY-BODY CALCULATIONS OF ENERGIES OF MG-I, AL-II, AL-I,HG-I, TL-II, TL-I, PB-I, BI-II AND BI-I

Energies of the low-lying excited states of six atomic systems with tw o electrons above the con (MgI, AlII HgI, TlII PbI, and BiII) and thre e systems with three electrons above the core (AlI TlI, and BiI) an de termined to second order in relativistic many-body perturbation theory using frozen-con Dirac-Hartree-Fock orbitals as a basis set. Ln the p resent report, the Breit interaction is included to first order only. Diagonalization of the effective Hamiltonian is carried out using two methods: (I) the symmetric first-order Hamiltonian (including both Cou lomb and Breit interactions) is diagonalized and then the second-order correlation is determined using the first-order eigenvectors; (II) th e first-order (Coulomb plus Breit) together with the non-symmetric sec ond-order effective Hamiltonian is diagonalized. Different model space s are considered Contributions from the three-electron interaction are compared with contributions from the two-and one-electron interaction s. Comparisons with experiment are made.