Ab initio calculation of the enhancement of the electric dipole moment of an electron in the YbF molecule

The (2) Sigma(+) ground state of the (YbF)-Yb-174-F-19 molecule is modelled in the unrestricted Dirac-Fock approximation. Molecular orbitals are taken to be linear combinations of kinetically balanced four-component spherical Gaussian spinors. The nuclei are assumed to be spherical distributions of charge, the radial dependences of which are taken to be Gaussian. Uncontracted basis sets with 27s, 27p, 12d and 8f exponents on the Yb centre and 15s and 10p exponents on the F centre yield an equilibrium bond length of R-e = 2.074 Angstrom, a dissociation energy of D-0 = 3.81 eV and a dipole polarizability of mu(e) = 4.00 D; the experimental values of these quantities are, respectively, R-e = 2.016 Angstrom. D-0 = 4.80-4.86 eV or greater than or equal to 5.36 eV, and mu(e) = 3.91(4) D. The matrix element of the operator -d(e)(gamma(0) -1)Sigma.E-mol, the interaction between an electronic electric dipole moment and the molecular electric field, is estimated to be -4.838d(e) atomic units within this approximation.