Fine-structure energy levels and lifetimes in Br XXIV

Abstract

We have performed large-scale CIV3 calculations of excitation energies from the ground state for 48 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the (1s22s22p6)3s2(1S), 3s3p(1,3Po), 3s3d(1,3D), 3s4s(1,3S), 3s4p(1,3Po), 3s4d(1,3D), 3s4f(1,3Fo), 3p2(1S, 3P, 1D), 3p3d(1,3Po, 1,3Do, 1,3Fo), 3p4s(1,3Po) and 3d2(1S, 3P, 1D) states of Br XXIV. These states are represented by extensive configuration-interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. The relativistic effects in intermediate coupling are incorporated by means of the Breit–Pauli Hamiltonian which consists of the non-relativistic term plus the one-body mass correction, Darwin term, and spin–orbit, spin-other-orbit and spin–spin operators. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimental values. Our calculated excitation energies, including their ordering, are in excellent agreement with the available experimental results except that the levels 1D2 and 3P2 belonging to the same configuration 3p2 interchanged their positions compared to the experiment. This interchange in our calculation is discussed and explained through eigenvector compositions of the two levels. From our radiative decay rates, we have calculated radiative lifetimes of some fine-structure levels. Our calculated lifetimes of the levels 3s3p(3P1) and 3s3p(1P1) are found to be in good agreement with the experimental and other theoretical results. In this calculation we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.