Towards 3D Exchange NMR in Solids
The 2D exchange NMR experiment for studying ultraslow molecular motions is extended to a third frequency dimension by employing two mixing times in combination with a frequency selection technique. This allows us to detect the orientation of selected ensembles of molecules at three subsequent times. The experiment yields a plane out of a full 3D spectrum. This offers so far inaccesible information about the pathway of a molecule during a dynamic process. In particular, degeneracies can be unravelled and the Markovian character of molecular motions can be checked explicitely.