Ionization potentials of alkali atoms: Towards meV accuracy

Ephraim Eliav, Marius J. Vilkas, Yasuyuki Ishikawa, Uzi Kaldor

Research output: Contribution to journalArticlepeer-review


Ionization potentials of orbitals in the three shells above the cation closed-shell structure (17 IPs per atom) are calculated for the alkali atoms Rb, Cs, Fr and element 119. The Dirac-Coulomb-Breit Hamiltonian is used as framework, and correlation is included by the multireference Fock-space coupled cluster method with single and double excitations. The basis includes 36s32p24d22f10g7h6i Gaussian-type orbitals. Comparison with the 45 experimentally known IPs shows excellent agreement, with an average absolute error of 11 cm-1 (1.4 meV) or 0.10% and maximum error of 81 cm -1 (10 meV) or 0.25%. The largest errors occur in the ground state IPs. Correcting for the Lamb shifts improves the s orbital binding energies, reducing the maximum error to 60 cm-1 (7.4 meV) or 0.19%. The remaining error is attributed to the truncation of the coupled cluster expansion and, to lesser extent, to small deficiencies in the basis.

Original languageEnglish
Pages (from-to)163-168
Number of pages6
JournalChemical Physics
Issue number1-2 SPEC.ISS.
StatePublished - 25 Apr 2005


  • Alkali atoms
  • Breit effect
  • Dirac-Coulomb-Breit Hamiltonian
  • Fock-space coupled cluster method
  • Ionization potentials
  • Lamb shift


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