Doublet inversions in alkali-metal spectra: Relativistic and correlation effects

Abstract

It is shown that in the central-field approximation, a relativistic calculation reproduces the inverted fine structures experimentally observed in the series of excited sodium $\mathrm{nd}\left(3\mathrm{}\le n\le 16\right)$ and cesium $\mathrm{nf}\left(4\mathrm{}\le n\le 12\right)$ terms. Theoretical results are in good agreement with measured values. In view of the simplicity of the method used, it can easily be applied to all the states of a given Rydberg series. This work brings to light the fact that a complete relativistic treatment (which introduces automatically the relativistic contributions on the large components of the wave functions) is equivalent to a multiconfigurational expansion of nonrelativistic wave functions taking into account relativistic corrections (in the low-$Z$ Pauli limit).