Excitation energies, E1, M1, and E2 transition rates, and lifetimes in Ca+, Sr+, Cd+, Ba+, and Hg+ 1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

Abstract

Excitation energies of ns1/2, npj, and ndj states in Cd+ (n = 5), Hg+ (n = 5) and ns1/2, npj, and (n – 1)dj states in Ca+ (n = 4), Sr+ (n = 5), and Ba+ (n = 6) are evaluated using the linearized coupled-cluster (all-order) method. Reduced matrix elements, oscillator strengths, and transition rates are determined for the ns–npj–ndj (or ns–npj–(n – 1)dj) possible electric dipole transitions in Ca+, Sr+, Ba+, Cd+, and Hg+. Electric quadrupole matrix elements are evaluated to obtain ns1/2–(n – 1)dj transition rates in Ca+ (n = 5), Sr+ (n = 5), and Ba+ (n = 6). The matrix elements are calculated using both relativistic many-body perturbation theory, complete through third order, and the relativistic all-order method restricted to single and double (SD) excitations. The SD lifetime results for the np and nd states in Ca+, Sr+, Ba+, Cd+, and Hg+, are compared with the latest available experimental measurements. The contribution of the magnetic dipole nd3/2–nd5/2 transition to the lifetimes of the lowest nd5/2 level ln Ca+, Sr+, and Ba+ ions is discussed. These calculations provide a theoretical benchmark for comparison with experiment and theory as well as data needed for various applications.