Effect of the structure of solid compounds on the shape of their NMR spectra and manifestations of dynamic chaos in paramagnetic spin systems

Resumo

The shape of NMR absorption line for typical ionic crystals, molecular crystals, and glasses is studied. The proposed theory and available experimental results suggest that the shape of NMR spectra of conventional dielectric crystals (and even molecular) is the convolution of a frequency-truncated nearly-rectangle-shaped function (characteristic oscillations in free precession signals) and a Gaussian-like function. A Gaussian-like shape of the spectra of glasses with a rigid structure (no oscillations in the free precession signal) is probably associated with a random scatter of interatomic distances. The results are interpreted within the framework of the proposed theory. It is demonstrated that, at least for solids the lattice of which contains no isolated groups of nuclei and are not quasi-one-dimensional, the structure only weakly affects the shape of the spectrum, which in turn is associated with the onset of dynamic chaos in the spin system.