The ground and first excited states of HoS studied by four-component relativistic KR-MCSCF and KRCI

摘要

The X(1)8.5 ground state and the W(1)7.5 first excited state of the HoS molecule are studied by the four-component Kramers-restricted multiconfiguration self-consistent field (KR-MCSCF) method, with an active space of (4f, 6s)(11), and then by the Kramers-restricted configuration interaction method with 27 electrons in Ho(5s), (5p), (4f), (6s), S(3s), and S(3p) correlated. For the X(1)8.5 state, R-e, omega(e), Delta G(1/2), and D-0 are calculated as 4.310 au, 477.385 cm(-1), 477.72 cm(-1), and 3.775 eV, respectively. The values of R-e and Delta G(1/2) agree well with the observed values of 4.301 au and 463.8811 cm(-1), respectively. The dominant configuration state function (CSF) is |(4f(5/2))(6) (4f(7/2,7/2))(1) (4f(7/2,5/2))(1) (4f(7/2,3/2))(1) (4f(7/2,1/2))(1) (6s(1/2,1/2))(1)|. This corresponds to the formal charge of Ho2+(I-5(8))S2-, representing ionic bonding where two electrons, one from [6s] and the other from [4f], are moved from Ho to S. In the doubly occupied S(3p) KR-MCSCF molecular spinors, hybridizations exist between S[3p] atomic spinors and Ho polarization functions [5d*] through which electrons are moved from S to Ho, resulting in covalent bonding. Consequently, ionic bonding is mixed with covalent bonding and 11 electrons of (4f, 6s) move outside the Ho13+([Xe])S2- ion core. The gross atomic charge of Ho is + 0.77 at the CI level. The excitation energy to the W(1)7.5 state is calculated as 0.027 eV, close to the experimental value of 0.031 eV.