MEASUREMENT OF QUADRUPOLAR COUPLING-CONSTANTS, SHIELDING TENSOR ELEMENTS, AND THE RELATIVE ORIENTATION OF QUADRUPOLAR AND SHIELDING TENSOR PRINCIPAL AXIS SYSTEMS FOR RB-87 AND RB-85 NUCLEI IN RUBIDIUM SALTS BY SOLID-STATE NUCLEAR MAGNETIC-RESONANCE

The spin lattice relaxation time, T1, quadrupolar coupling constant, Qcc, and chemical shielding tensor elements of several rubidium salts have been surveyed at the frequency 130.88 MHz for 87Rb and 38.64 MHz for 85Rb, i.e. 9.4T, or 400 MHz for 1H's. Typical relaxation times for 87Rb are in the range of 100-300 ms and 50-300 ms for 85Rb. The Qcc. values are in the range of 7-14 MHz for 85Rb and 3-11 MHz for 87Rb. A program was created to numerically simulate and fit experimental powder patterns for the ±1/2 central transition, where the principal axis systems (PAS) of the shielding and quadrupole tensors are not coincident. The analysis shows that having both nuclides available with significantly different quadrupole coupling constants makes the general line-shape problem more tractable. That is, the 85Rb data provides an excellent visualization of chemically different rubidium atoms when there are significant differences in the value of Qcc. Such data would be difficult to extract from the corresponding 87Rb line shapes due to the smaller value of Qcc. The 87Rb nuclide, however, because of its smaller value of Qcc, provides an excellent opportunity to observe the consequences of the noncoincident PAS frames between the shielding and quadrupole tensors. © 1990 American Chemical Society.