2D CP/MAS 13C isotropic chemical shift correlation established by 1H spin diffusion

A new 2D solid-state CP/MAS C-13 NMR exchange experiment for through-space isotropic chemical shift correlation is proposed and demonstrated. Through-space correlation is established via a second cross polarization 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 allowing different mean square magnetization displacements to be probed. Experimental results on mixtures of differently C-13-labeled alanine and polyethylene indicate that this site-selective 2D technique can be used to characterize domain sizes and proximities over a wide range of length scales (1-200 nm) in solids such as polymers or biological materials. (C) 1998 Academic Press.