MAPPING MOLECULAR-ORIENTATION BY SOLID-STATE NMR IMAGING

A new solid-state NMR imaging experiment is presented which provides high-resolution chemical-shift selective images of abundant nuclei. This experiment employs the line-narrowing effects of the TREV-8 pulse sequence and a constant-time phase-encoding period to achieve spatial resolution. At the end of the phase-encoding period, however, the chemical-shift evolution is reversed and an echo is recorded during the subsequent acquisition period. A 3D data set is acquired which, after processing, results in one 2D image for each point in the chemical-shift spectrum. A single vector passing through all of the images provides a dipolar-decoupled NMR spectrum for any picture element in the image. This method has been applied to monitor the propagation of stress during crack growth in polytetrafluoroethylene. (C) 1994 Academic Press, Inc.