THE RELIABILITY OF THE DETERMINATION OF TENSOR PARAMETERS BY SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE

The accuracy of determination of tensor parameters measured using soli d-state nuclear magnetic resonance is investigated. In particular, the reliability of the determination of the anisotropy and the asymmetry parameter of the chemical shift is calculated using the Cramer-Rao low er bounds. Minimizing this measure of the error as a function of an ex perimental parameter (in this case the spinning speed of the sample) e nables the optimization of any given experiment. Hence, an optimum num ber of sidebands is found for which the determination of the anisotrop y is most reliable. Comparision to the static limit shows that the rel iability of the determination of the anisotropy is always greater in s pinning experiments than in static experiments. An analogous analysis for the asymmetry parameter shows it to be consistently more reliably determined from a static spectrum. The sensitivity of the fitting to t he simulation algorithm is found to become pronounced with slower spee ds and static spectra, and a discussion of such systematic errors is p rovided. The reliability of the determination of dipolar or first-orde r quadrupolar tensors is also calculated, and we find that this presen ts a surprisingly different situation to that of the chemical shift. ( C) 1997 American Institute of Physics.