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 d(10) to d(9) levels. Thus the d(10)s-->d(9)s(2) energy of E113(2+) is 0.1 eV, compared to 8 eV for Tl2+. It is predicted that divalent or trivalent compounds of E113 with an open 6d(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.