Oscillator strengths and lifetimes in Ge XXI

Abstract

We have calculated energy splittings of 53 fine-structure levels as well as 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,3F,1G) states of Ge XXI, using extensive configuration–interaction (CI) wavefunctions, obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit–Pauli Hamiltonian. In order to keep our calculated energy splittings as close as possible to the experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Our excitation energies, including their ordering, are in excellent agreement with the available experimental results. The enormous mixing among several fine-structure levels makes it very difficult to identify them correctly with the result that their positions in the calculation of Ivanova et al are interchanged compared to our results and the experimental values. From our transition probabilities, we have also calculated radiative lifetimes of some fine-structure levels. Our calculated oscillator strengths and the lifetimes are found to be in good agreement with the other available theoretical results. In this calculation, we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available.