Semiempirical valence bond model of hyperfine interactions and bonding in RbO and CsO

The alkali hyperfine structure (hfs) splittings in the 2Σ radicals RbO and CsO are analyzed using a semiempirical valence bond (VB) wave function similar to that used previously for the noble gas monohalides. For the alkali monoxides this wave function is ψ=N(2Σ)[χAΦ(M+ ⋅ ⋅ ⋅ O−) +(1−χ2)1/2AΦ(M++ ⋅ ⋅ ⋅ O=)], where M and O denote the alkali and oxygen, respectively, and A is the antisymmetrization operator. This antisymmetrization and the effects of interatomic electron correlation in the Φ(M++ ⋅ ⋅ ⋅ O=) VB structure are the principal contributors to the hfs. At the bond distances RRbO=4.30 and RCsO=4.67a0 the parameters χ=0.9996 and 0.9967 for RbO and CsO, respectively, give good agreement between theory and experiment for both the isotropic and anisotropic hfs. The admixture of the doubly ionized Φ(M++ ⋅ ⋅ ⋅ O=) VB structure, which produces covalent bonding involving the alkali cation core orbitals and the oxygen anion valence orbitals, is small as expected from the high energy of this structure.

[1]  D. Case,et al.  Relativistic effects on molecular hyperfine interactions: Application to XeF and CsO , 1983 .

[2]  Per E. M. Siegbahn,et al.  Theoretical determination of the X2Σ+ and A2Π potentials of CsO using relativistic effective core potentials , 1983 .

[3]  William A. Goddard,et al.  Alkali oxide diatomics: Explanation of the change in ground state symmetry from LiO(2Π) CsO(2Σ+) , 1982 .

[4]  A. N. Jette,et al.  Anisotropic hyperfine interactions of rare‐gas nuclei near trapped hydrogen atomsa) , 1979 .

[5]  A. N. Jette,et al.  Valence bond study of hyperfine interactions and structure of the noble gas monohalides , 1978 .

[6]  M. Krauss,et al.  The energy curve of XeF, X 2Σ+ , 1976 .

[7]  A. N. Jette,et al.  Theoretical investigation of the hyperfine-structure constants of theVKand(XY)−centers using a valence-bond wave function for the halogen-molecule anions , 1976 .

[8]  P. Hay,et al.  Electronic states of KrF , 1976 .

[9]  W. G. Richards,et al.  The electronic ground states of alkali monoxides , 1975 .

[10]  Dudley R. Herschbach,et al.  ESR spectra of matrix isolated CsO and RbO molecules: 2Σ ground states and inner shell bonding , 1974 .

[11]  H. Schaefer,et al.  Probable nonexistence of xenon monofluoride as a chemically bound species in the gas phase , 1973 .

[12]  H. Schaefer,et al.  Krypton Monofluoride and Its Positive Ion , 1971 .

[13]  D. Herschbach,et al.  Molecular Beam Kinetics: Reactions of Alkali Atoms with NO2 and CH3NO2 , 1970 .

[14]  J. Bearden,et al.  Atomic energy levels , 1965 .

[15]  H. Casimir.  On the interaction between atomic nuclei and electrons , 1936 .