A full configuration interaction calculation of the density dependence of the ³He shielding constant

Abstract

The interaction-induced changes in the ³He shielding constant of the helium dimer have been calculated using the full configuration interaction method and large basis sets. From these data the first virial coefficient for the ³He isotropic shielding constant in gaseous helium has been determined. At room temperature it is negligibly small, approximately −0.006 cm³ mol⁻¹ and it increases monotonically with temperature. This behaviour is caused by the monotonic dependence of the isotropic shielding constant of He₂ on the interatomic distance. In addition. the non-relativistic value of the shielding constant of the isolated He atom was estimated to be σ^iso = 59.932 ppm.