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 exci tation energies of Tl and element 113 and their cations. Large basis s ets are used, with l up to 6, the Dirac-Fock or Dirac-Fock-Breit orbit als found, and the external 35 electrons of each atom are correlated b y the coupled-cluster method with single and double excitations. Very good agreement with experiment is obtained for the Tl transition energ ies. 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 o bserved for E113, leading to dramatic reduction (relative to Tl) in th e 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 i s predicted that divalent or trivalent compounds of E113 with an open 6d(9) shell could possibly exist. The calculated electron affinities o f Tl and E113 are 0.40+/-0.05 and 0.6-0.7 eV, respectively.