Anisotropy of the nuclear spin coupling in PHminus;2, PH3, and PH+4molecules

摘要

The anisotropy of the nuclear spinndash;spin coupling tensor, relative to P, H and H, H interacting nuclei, has been investigated by means of extendedabinitiocalculations in the molecules PHminus;2, PH3, and PH+4. The coupled Hartreendash;Fock perturbed scheme has been employed retaining the nonrelativistic Ramsey Hamiltonians. The most important contributions to the anisotropy in the P, H coupling arise from the Fermi contacthyphen;spinhyphen;dipolar cross term, which is partially counterbalanced by the spinhyphen;orbit effect. The discrepancies emerging between computed and experimentalJ(P,H) in phosphine and phosphonium are interpreted in terms of neglected electron correlation contributions. A dramatic sensitivity of the Fermi contact term of the molecular geometry has been found for PH2minus;. The calculations show that the Pndash;H coupling is more anisotropic than Nndash;H, which is seemingly due to the enhanced nonsphericity of electron distribution.