Structural relaxation of the fragile glass-former propylene carbonate studied by nuclear magnetic resonance

Proton, deuteron, and carbon NMR methods were applied to study various isot opic species of supercooled and glassy propylene carbonate. The molecular d iffusion was investigated via static field gradient diffusometry and yielde d evidence for a particularly pronounced enhancement of the translational o ver the reorientational dynamics. The latter was monitored using measuremen ts of spin-lattice relaxation times and of two-time stimulated echoes. The sin-sin correlation functions exhibited a pronounced dependence on the evol ution times. From these results it is concluded that the geometry of molecu lar reorientation can be described as a superposition of moderately small j ump angles (about 30 degrees) and a quasi-diffusive component which is resp onsible for about one-third of the total angular displacement. Finally, fou r-time stimulated echoes confirmed that the nonexponential relaxation in pr opylene carbonate is dynamically heterogeneous in nature. (C) 2000 American Institute of Physics. [S0021-9606(00)50821-6].