Recent developments in the mathematical solution of nuclear magnetic ( ) resonance NMR relaxation equations describing rotational motion allow investigators to determine correlation times, , on the nanosecond time scale. NMR rotational correlation equations for quadrupolar and dipolar relaxation can be solved for nuclei in moderately viscous media using R / R ratios. In the case of quadrupolar nuclei, the R / R ratios can 2 1 2 1 be used to solve the rotational correlation equations directly. For dipolar nuclei including 1 H, 13 C, 15 N, 19 F, 31 P, and 113 Cd, it is necessary to solve the rotational correlation time equations at each magnetic field strength using iterative methods. The resulting solutions ( ) are fitted to pairs of polynomials R / R = 1.1 α 20 and 20 α 1200 at individual magnetic 2 1 ( ) field strengths 4.7, 6.35, 7.05, 9.4, 11.75, and 14.1 T . The investigator determines the R / R 2 1 ratio at a specific magnetic field and uses the appropriate polynomial to determine the rotational correlation time. Correlation times are used to study molecular interactions where dipolar relaxation occurs and to determine quadrupole coupling constants, , where quadrupole relaxation is the predominant mechanism. 1 H-NMR diffusion constants can be compared with NMR correlation times to provide data about the transport properties of the system being studied.