Theoretical Investigation of the Ge Isoelectronic Sequence

We aim to present first large scale and systematic investigation on atomic properties of Ge-like ions: As¹⁺, Se²⁺, Br³⁺, and Kr⁴⁺. The multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods, which are implemented in the general-purpose relativistic atomic structure package Grasp2018, are used in the present work. We computed the energy levels of the 4s² 4p², 4s4p³, 4p⁴, 4s² 4p {5s, 6s, 5p, 6p, 4d, 5d, 4f}, and 4s4p² {4d, 5s} configurations and the electric dipole, magnetic dipole, and electric quadrupole transitions between states of these configurations. The accuracy of energy levels is evaluated by comparing our results with the recommended values of the National Institute of Standards and Technology Atomic Spectra Database and with energy levels estimated with various methods. The accuracy of transition data is investigated using the quantitative and qualitative evaluation method. We applied our results to astrophysics by constructing the list of M1-type transitions for kilonova. For Ge-like ions presented in this paper, we confirmed that the transition list assuming the LS-coupling selection rules, as adopted in the previous studies, includes all the important transitions and that an analytical formula for transition probabilities gives a good accuracy.