Coherent averaging techniques are used to examine the 19F shielding tensors of the trifluoromethyl group in single crystals of silver trifluoroacetate. At room temperature, where the CF3 groups are rotating rapidly, the spectrum consists of a single line whose orientation dependence allows a determination of the orientation of the CF3 groups in the unit cell. The rigid lattice (40°K) spectra exhibit the six lines expected on the basis of the x-ray crystal structure, also determined in this work, and allow a determination of all six independent elements of each of the three incongruent chemical shift tensors.
The phase-alternated experiment in liquids, a multiple-pulse NMR experiment capable of scaling chemical shifts, is examined theoretically and experimentally. The theory of the experiment is worked out using both the average-Hamiltonian and classical magnetic-dipole techniques, and the results from the two methods are compared. The effects of nonideal pulse cycles are discussed. Theoretical results are compared with experimental data, and a high-resolution NMR spectrum with scaled chemical shifts is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.