Translational and Rotational Diffusion Near the Glass Transition

摘要: Diffusional transport is involved in most relaxation processes condensed matter. In one component systems this usually termed “self- diffusion” since the molecules move among themselves. Nevertheless some kind of labeling must be possible order to observe “tracer” moving relative their neighbors. The best labels for self diffusion experiments are nuclear spin states used NMR methods described below. all other techniques, motion tracer somewhat different from that environment and should, strictly speaking, “tracer-diffusion”. corresponding self- or tracer-diffusion coefficients related mean square displacement position r(t) by $$D = \frac{{\lim }}{{t \to \infty }}\,\{ \langle [r(t) - r(0)]^2 \rangle /6t\} \,,$$ (3.1)