Transition energies of barium and radium by the relativistic coupled-cluster method

Ephraim Eliav, Uzi Kaldor, Yasuyuki Ishikawa

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The relativistic coupled-cluster method is used to calculate ionization potentials and excitation energies of the barium and radium atoms and their monocations. Large basis sets are used, with l up to 5, the Dirac-Fock or Dirac-Fock-Breit orbitals found, and the external 28 electrons of barium or 42 electrons of radium are correlated by the coupled-cluster method with single and double excitations. Good agreement (within a few hundred wave numbers) is obtained for the ionization potentials and low excitation energies (up to 3 eV for Ba, 4 eV for Ra). The Breit interaction has little effect on the excitation energies, but it improves significantly the fine-structure splittings of Ra. Large relativistic effects on the energies are observed, up to 1 eV for barium and 2 eV for radium. The nonrelativistic ground states of [Formula Presented] and [Formula Presented] are (n-1)d [Formula Presented]D rather than ns [Formula Presented]S.

Original languageEnglish
Pages (from-to)3050-3056
Number of pages7
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number5
StatePublished - 1996


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