Perturbation theory of the electron correlation effects for atomic and molecular properties IV. Dipole polarizability of the fluoride ion

The fourth order many-body perturbation theory restricted to single and double excitations from the Hartree-Fock determinant is used for the calculation of correlation corrections to the dipole polarizability of the fluoride ion. The present results confirm previous suggestions concerning the magnitude and sign of the total correlation correction to the coupled Hartree-Fock result. The correlation perturbation series for the fluoride ion polarizability is found to converge very slowly and the total correction is evaluated by using two different summation schemes. The final polarizability values that follow from these two procedures are 16·0 e 2 a 0 2 E h −1 and 15·1 e 2 a 0 2 E h −1 with some preference given to the lower result. The available empirical estimates are in most cases much lower than the computed values and the sources of this discrepancy are discussed. It is argued that all empirical values of the fluoride ion polarizability are considerably contaminated by the effects of the ion surrounding and do not correspond to the free ion polarizability. A method for the experimental verification of this suggestion is proposed.