A PERTURBATION CALCULATION OF THE EFFECT OF ELECTRIC INTERACTION ON PROTON MAGNETIC SHIELDING

The effect of electric interaction of molecular systems on proton magnetic shielding is calculated by a perturbation method, and a general expression of this effect is obtained. It is shown that the effect consists of three parts. Two of them are dependent on the time average of the field at the proton, and correspond to the linear and the square terms of Buckingham's equation of the (external) electric field effect. The third part is proportional to the van der Waals interaction energy between the hydrogen and the interacting object. The magnitude of the former two terms is calculated for a polarized hydrogen atom and a hydrogen molecule. The van der Waals deshielding caused by halogen atoms is also estimated.