Relativistic configuration-interaction and many-body-perturbation-theory calculations of U I hyperfine constants

摘要: Neutral uranium (U i) is a very difficult atom for theoretical calculations due to large number (six) of valence electrons, strong valence-valence and valence-core correlations, high density states, relativistic effects. Configuration-interaction many-body perturbation theory (CI-MBPT) can efficiently treat correlations effects, but because the formalism was developed Dirac-Hartree-Fock (DHF) starting potential that does not contain quite CI space needed compensate $+6$ charge such potential. Much more efficient configuration-interaction (RCI) approach, which uses relatively accurate DHF includes some electrons make valence-electron Hamiltonian diagonally dominated states. Here we report U i hyperfine constants several low-energy states using RCI method with four $f$ electrons. With this potential, it possible use single-configuration approximation or small basis sets obtain results hyperfine-structure constants. In fact, by scaling nuclear magnetic moment, agreement five levels within 5% new moment be recommended, 0.43(2). When two are mixed, predict exact mixing fractions, so in case proposed fraction found optimization one parameter MBPT correction correct $g$ factors. The resulting significantly improved. Finally, CI-MBPT approach also tested, success limited set. methods investigated here further include extensive data improve accuracy applied other atoms properties, example, relevant fundamental symmetry tests.