ELECTRIC-DIPOLE MOMENT OF THE ELECTRON IN THE YBF MOLECULE

We have performed an ab initio calculation of the hyperfine, P-odd and P, T-odd constants for the YbF molecule using a recently developed te chnique which allows us to take into account correlations and polariza tion in the outer-core region. The ground state ((2)Sigma(1/2)) electr onic wavefunction of the YbF molecule is found with the help of the re lativistic effective core potential method followed by the restoration of molecular four-component spinors in the core region of ytterbium w ithin the framework of a non-variational procedure. Core polarization effects are included with the help of atomic many-body perturbation th eory for the Yb atom. Our calculation of the isotropic hyperfine const ant A agrees at the 3% level with the experimental value. The dipole c onstant A(d) (which is much smaller in magnitude), though better than in all previous calculations, is still underestimated by almost 23%. T his error is reduced to 8% after a semiempirical correction for pertur bation of the 4f-shell in the core of Yb due to the chemical bonding m ade. Our value for the effective electric field on the unpaired electr on is 4.9 au = 2.5 x 10(10) V cm(-1).