Correlation and relativistic effects in actinide ions

Abstract

Wavelengths, line strengths, and transition rates are calculated for the multipole ($E1$, $M1$, $E2$, $M2$, $E3$, and $M3$) transitions between the excited $6{s}^{2}6{p}^{5}nl$ and $6s6{p}^{6}nl$ states and the ground $6{s}^{2}6{p}^{6}$ state in Ac${}^{3+}$, Th${}^{4+}$, and U${}^{6+}$ Rn-like ions. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in these hole-particle systems. The RMBPT method agrees with multiconfigurational Dirac-Fock (MCDF) calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative-energy states. The calculations start from a [Xe]$4{f}^{14}5{d}^{10}6{s}^{2}6{p}^{6}$ Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. Evaluated multipole matrix elements for transitions from excited states to the ground states are used to determine the line strengths, transition rates, and multipole polarizabilities. This work provides a number of yet unmeasured properties of these actinide ions for various applications and for benchmark tests of theory and experiment.