The fine-structure splitting of the thallium atomic ground state: LS- versus jj-coupling
✍ Scribed by Frank Rakowitz; Christel M. Marian
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 483 KB
- Volume
- 257
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
We examine the spin-orbit splitting of the 2p electronic ground state of the TI atom by two different approaches, both of which incorporate relativistic effects: namely, a four-component method involving the Dirac-Coulomb-Breit Hamiltonian, and a two-component method which makes use of the Douglas-Kroll transformed no-pair Hamiltonian, The former method operates by definition in the jj-coupling scheme, while the latter uses LS-coupled states. The four-component method is found to work well provided that separate orbital optimizations are performed for the 1/2(I) and 3/2(•) 2p sublevels. In the LS-coupling scheme consideration of the spin-orbit splitting by perturbation theory fails, while inclusion of spin-orbit interaction in a variational procedure yields a good result. The reason for the failure of perturbation theory lies in the large difference of the spatial extensions of the P3/2 and Pl/2 valence orbitals of the TI atom.