Calculated energy levels of thallium and eka-thallium (element 113)

Multiconfiguration Dirac-Fock and relativistic coupled cluster results are reported for electron affinities, ionization potentials, and excitation energies of Tl and element 113 and their cations. Large basis sets are used, with l up to 6, the Dirac-Fock or Dirac-Fock-Breit orbitals found, and the external 35 electrons of each atom are correlated by the coupled-cluster method with single and double excitations. Very good agreement with experiment is obtained for the Tl transition energies. As in the case of elements 111 [Eliav et al., Phys. Rev. Lett. 73, 3203 (1994)] and 112 [Eliav, Kaldor, and Ishikawa, Phys. Rev. A 52, 2765 (1995)], strong relativistic stabilization of the 7s orbital is observed for E113, leading to dramatic reduction (relative to Tl) in the energies of excitation from ${\mathit{d}}^{10}$ to ${\mathit{d}}^9$ levels. Thus the ${\mathit{d}}^{10}$s→${\mathit{d}}^9$ ${\mathit{s}}^2$ energy of ${\mathrm{E}113\mathrm{}}^{2+}$ is 0.1 eV, compared to 8 eV for ${\mathrm{Tl}}^{2+}$. It is predicted that divalent or trivalent compounds of E113 with an open 6${\mathit{d}}^9$ shell could possibly exist. The calculated electron affinities of Tl and E113 are 0.40±0.05 and 0.6–0.7 eV, respectively. © 1996 The American Physical Society.