Combined reduced 4D C-13 exchange and H-1 spin diffusion experiment for determining the length scale of dynamic heterogeneities

A multidimensional static solid-state NMR experiment is described that comb ines C-13 exchange sequences with H-1 spin diffusion. It realizes a spatial correlation of different reorientation rates. By means of this experiment the length scale of dynamic heterogeneities can be measured directly, The p ulse sequence and phase cycle as well as the experimental setup procedure a nd data analysis are described in detail. It complements the previous lette r on this subject where a brief report of the main results were presented ( U, Tracht et at, 1998, Phys. Rev. Lett. 81, 2727), Application of this expe riment to an amorphous polymer in the supercooled state yields a length sca le of immobile regions of about 3 nm, (C) 1999 Academic Press.