2. HR PMR EXPERIMENTS

The High Resolution Proton Magnetic Resonance (HR PMR) experiments in Solids have been well described in the literature². It is reiterated here that the single specimen used for the measurements in HR PMR in solids have been spherically shaped; for reasons that the bulk susceptibility contribution to induced fields within the specimen is zero for the spherical shape of the specimen. This limits the utility of this technique since it is not always possible that the given organic molecular single crystal can be shaped into a sphere for the convenient use for measurement by HR PMR techniques. The current experimental efforts being made to reduce the experimental constraints in making spheres are posted in the WebPages³ of this author. Fig.1 below depicts the situation for the disposition of the experimentally measured principal axis directions of the chemical shift tensor for the proton attached to the aromatic ring and the deviation from the molecular symmetry is obvious in the Fig.1 (a) and when the intermolecular contribution is subtracted then the principal directions conform better to the molecular symmetry requirements

 

              

 

The considerations which are also pertinent to consequences in magnetic material begin with this effort by which the intermolecular contributions were calculated by rigid lattice summation procedures.