Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Ge II*

Better understanding of the atomic structure for atomic ions requires experimental measurements for lifetimes and oscillator strengths which also serve as a test for theoretical calculations. Furthermore, interpreting astronomical observations of atomic ions requires knowledge of their oscillator strengths and transition probabilities. We present the results of lifetime measurements with beam-foil techniques performed with the Toledo Heavy-Ion Accelerator on levels of interest in Ge~{\footnotesize II} producing transitions to the ground term at 1237.1 {\AA} and 1261.9 {\AA} ($4s^{2}4d$ $^{2}D_{3/2}$ and $4s^{2}4d$ $^{2}D_{5/2}$, respectively). Oscillator strengths are derived from the lifetimes, and our experimental results are compared with our MCDHF\footnote[2] {P. J{\"{o}}nsson et al., The Computational Atomic Structure Group (2014)} calculations using the development version of the GRASP2K package\footnote[3] {P. J{\"{o}}nsson et al., Comput. Phys. Commun. 184, 2197 (2013)} as well as the latest calculations done by others. We also provide an overall comparison of our studies on the $ns^{2}nd$ $^{2}D$ and $nsnp^{2}$ $^{2}D$ terms in three elements of group~{\footnotesize IV} of the periodic table, namely Pb~{\footnotesize II}, Sn~{\footnotesize II} and Ge~{\footnotesize II}.