SIMULATION OF NMR POWDER LINE-SHAPES OF QUADRUPOLAR NUCLEI WITH HALF-INTEGER SPIN AT LOW-SYMMETRY SITES

At crystallographic sites of low symmetry it is possible for the interactions governing the NMR powder line shape of half-integer spin quadrupolar nuclei to have different orientation dependences. In such cases, it is found that the NMR line shape is sensitive to the relative orientation of the quadrupolar (Q) and chemical shielding (CS) tensors. An analysis of the 133Cs NMR powder pattern of cesium chromate illustrates the importance of considering such orientation effects. For systems where second-order quadrupolar interactions influence the central (mI = 1/2 ↔ -1/2) transition, the line shape arising from this transition also depends critically on the relative orientation of the Q and CS tensors. It is anticipated that such effects will be important for spin n/2 nuclei (n = 3, 5, 7, or 9) with large chemical shift ranges and quadrupole moments larger than that of 133Cs (e.g., 17O, 51V, 59Co, and 63Cu). © 1990 American Chemical Society.