The effect of intermolecular interactions on t he electric properties of helium and argon. Part III: Quantum statistical calculations of the dielectric s econd virial coefficients.

The second dielectric virial coefficients of helium and argon are investigated using a fully quantum statistical approach and recent accurate {\it{ab initio}} results for the interatomic potentials and the interaction-induced polarizabilities. We thereby extent a preceding investigation based on a semiclassical approach to include quantum effects. For helium the results support the findings of a previous study by Moszynski {\em{et al.}} [J. Chem. Phys., {\bf{247}}, 440, (1995)] that quantum effects are substantial for temperatures below 10~K, while they are practically negligible above 70~K. For argon special care is needed in the numerical integrations carried out in the quantum statistical calculation of the virial coefficients, due to the presence of quasi-bound states in the continuum and a slow convergence of the summation over the angular momentum. Here quantum effects are practically negligible in the range of temperatures experimentally investigated, i.e. between 243 and 408~K. As far as comparison with experimental data is concerned, large discrepancies are found for some of the low--temperature experimental measurements of helium. Agreement is also unsatisfactory for high temperatures for Argon and experimental redetermination is suggested.