SAMPLE-SHAPE DEPENDENCE OF THE INHOMOGENEOUS NMR LINE BROADENING AND LINE SHIFT IN DIAMAGNETIC LIQUIDS

In diamagnetic solutions, we determine the frequency shift and the inhomogeneous broadening of high-resolution NMR lines of nuclei I due to the dipolar interactions with the molecular electronic magnetic moments induced by the external magnetic field. This effect, which depends on the shape of the liquid sample, arises from the inhomogeneous demagnetizing field and is theoretically studied for various geometries. It results in considerable shifts and linewidths of several ppm. Experiments are performed on proton NMR spectra of tetramethylammonium ions in heavy water, and of liquid benzene. Good agreement with theory is obtained.