Benchmark calculations of electron affinities of the alkali atoms sodium to eka-francium (element 119)

Electron affinities of the alkali atoms sodium to eka-francium are calculat ed by the intermediate Hamiltonian Fock-space coupled cluster approach, whi ch allows very large P spaces. Large basis sets are used (37s32p23d18f10g7h for most atoms), and many electrons are correlated (from 10 for Na- to 52 for E119(-)) to account for core polarization. While the usual Fock-space m ethod gives errors of 5%-9% for K, Rb, and Cs, the intermediate Hamiltonian results agree with all known values to 5 meV or 1%. The EA of Fr, not know n experimentally, is predicted at 491+/-5 meV. While EAs decrease from Li t o Cs, the Fr value is 20 meV higher than that of Cs, with E119 EA being muc h higher at 662 meV. This trend reversal is due to relativistic stabilizati on of s orbitals, which has been shown [Eliav , Phys. Rev. Lett. 74, 1079 ( 1995)] to give the rare gas E118 positive electron affinity. (C) 2001 Ameri can Institute of Physics.