Lifetimes and oscillator strengths for ultraviolet transitions in singly-ionized germanium

The results of lifetime measurements using beam-foil techniques for the 4 s 2 4 d 2 D 3 2,5 2 levels in Ge ii are presented. The corresponding oscillator strengths for transitions at 1237.1, 1264.7 and 1261.9 are derived and reported. These levels, as well as the 4 s 4 p 2 2 D 3 2,5 2 levels, are studied with multi-configuration Dirac-Hartree-Fock calculations using a development version of the GRASP2K package. The resulting energy levels from our calculations are reported in this paper. These calculations aid and extend the laboratory results. Our experimental and theoretical results are compared with other available studies.