title: Solution of the Dirac Coulomb equation for helium-like ions in the Poet-Temkin model.
abstract: The Dirac-Coulomb equation for the helium atom is studied under the restrictions of the Poet-Temkin model which replaces the 1/r12 interaction by the simplified 1/r> form. The effective reduction in the dimensionality made it possible to obtain binding energies for the singlet and triplet states in this model problem with a relative precision from 10(-8) to 10(-10). The energies for the singlet state were consistent with a previous configuration interaction calculation [H. Tatewaki and Y. Watanabe, Chem. Phys. 389, 58 (2011)]. Manifestations of Brown-Ravenhall disease were noted at higher values of nuclear charge and ultimately limited the accuracy of the Poet-Temkin model energy. The energies from a no-pair configuration interaction (CI) calculation (the negative-energy states for the appropriate hydrogen-like ion were excluded from the CI expansion) were found to be different from the unrestricted B-spline calculation.
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
authors.forename: Li-Yan
authors.initials: LY
authors.lastname: Tang
authors.forename: Yong-Bo
authors.initials: YB
authors.lastname: Tang
authors.forename: Ting-Yun
authors.initials: TY
authors.lastname: Shi
authors.forename: J
authors.initials: J
authors.lastname: Mitroy