The use of sample rotation for minimizing convection effects in self-diffusion NMR measurements

Undesirable temperature gradients in a NMR sample tube are usually generate d by an inappropiate temperature regulation system. We have shown that such convection effects can greatly distort the measurement of translational se lf-diffusion coefficients. The use of sample spinning helps to minimize suc h undesirable effects by disruption of convection fluxes due to resulting C oriolis forces that have a strongly stabilizing effect on the conducting st ate of the system (J. Lounila et al., J. Magn. Reson. A 118, 50 (1996)). Th is simple trick allows the accurate measurement of diffusion coefficients f or a wide range of temperatures and solvents without the need for a convect ion-compensated NMR pulse sequences or more sophisticated temperature contr ol units. Experimental data obtained for some target compounds dissolved in several common deuterated solvents at different temperatures are reported and discussed. (C) 2001 Academic Press.