Diffusion Selective Pulses

Abstract

The self-diffusion coefficient, D, provides important chemical and physical information about a molecular species and its environment, and D can be routinely measured under equilibrium conditions using nuclear magnetic resonance (NMR). Differences in diffusion coefficients can also be exploited in NMR to suppress signals from fast diffusing species relative to slow diffusing species. To date, no method for selectively suppressing signals only from species with a particular diffusion coefficient has been presented. In this work, diffusion selective pulses are developed that selectively suppress the magnetization only from species for which D = DSel. This is accomplished by interleaving NMR relaxation selective pulses between pulsed field gradients, where the effective transverse relaxation of the magnetization is related to D. Experimental demonstrations of diffusion selective pulses on water and water/acetone/dimethyl sulfoxide samples and on a magnetic resonance imaging phantom are presented.