2D CP MAS C-13 ISOTROPIC CHEMICAL-SHIFT CORRELATION ESTABLISHED BY H-1 SPIN-DIFFUSION/

A new 2D solid-state CP/MAS C-13 NMR exchange experiment for through-s pace isotropic chemical shift correlation is proposed and demonstrated . Through-space correlation is established via a second cross polariza tion from C-13 to H-1 and subsequent H-1 spin diffusion. A third cross polarization results in the final C-13-C-13 isotropic chemical shift correlation. The H-1 spin diffusion time is a variable parameter allow ing different mean square magnetization displacements to be probed. Ex perimental results on mixtures of differently C-13-labeled alanine and polyethylene indicate that this site-selective 2D technique can be us ed to characterize domain sizes and proximities over a wide range of l ength scales (1-200 nm) in solids such as polymers or biological mater ials. (C) 1998 Academic Press.