Combined Reduced 4D C Exchange and H Spin Diffusion Experiment for Determining the Length Scale of Dynamic Heterogeneities

A multidimensional static solid-state NMR experiment is described that combines 13C exchange sequences with 1H 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 pulse sequence and phase cycle as well as the experimental setup procedure and data analysis are described in detail. It complements the previous letter on this subject where a brief report of the main results were presented (U. Tracht et al., 1998, Phys. Rev. Lett. 81, 2727). Application of this experiment to an amorphous polymer in the supercooled state yields a length scale of immobile regions of about 3 nm.