Theory of negative fine and hyperfine structure in excited states of rubidium:4D2state

Abstract

The negative signs of the fine-structure constant and dipolar and contact hyperfine constants for the $4{}_{}{}^2{}_{}{}^{}D$ state of the rubidium atom are all explained by the common mechanism of exchange polarization of core states by the valence $4d$ state. The results of the present one-electron theory for the fine-structure, dipolar, and contact hyperfine structure constants are -3.7 (6.1 - 9.7) ${\mathrm{cm}}^{-1\mathrm{}}$, -0.37 (0.29 - 0.65) × ${10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$, and -2.1 (0.0 - 2.1) × ${10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$, respectively, where the values given in parentheses are, first, the (restricted) Hartree-Fock and, second, the exchange core-polarization contributions. By including the exchange core-polarization contribution, the resulting estimates are in reasonable accord with the corresponding observed values of these coupling constants: -0.176 ${\mathrm{cm}}^{-1\mathrm{}}$, -0.318 × ${10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$, and -4.22 × ${10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$, respectively. The possible importance of many-body and relativistic effects is discussed.