Search

Energies of the 148 (3l3l'3l") states for aluminiumlike ions with Z=14-100 are evaluated to second order in relativistic many-body perturbation theory. Second-order Coulomb and Breit-Coulomb interactions are included. Corrections are made to lowest order for the frequency-dependent Breit interaction and for the Lamb shift. A detailed discussion of the various contributions to the energy levels is given for aluminiumlike germanium (Z=32). Comparisons of the calculated energy levels with available experimental data are made for the entire sequence.

A relativistic many-body method is developed to calculate energy and transition rates for multipole transitions in many-electron ions. This method is based on relativistic many-body perturbation theory (MBPT), agrees with MCDF calculations in lowest-order, includes all second-order correlation corrections, includes corrections from negative energy states, and is gauge independent. Reduced matrix elements, oscillator strengths, and transition rates are calculated for electric dipole (E1) and quadrupole (E2) transitions and magnetic dipole (M1) and quadrupole (M2) transitions in Ne-like ions with nuclear charges ranging from Z = 11 to 100. The calculations start from a 1s{^2}2s{^2}2p{^6} Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order MBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order E1, M1, E2 and M2 matrix elements. The resulting transition energies and transition rates are compared with experimental values and with results from other recent calculations

Second-order [O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms;Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.