Relaxation time studies of AFC

1 Distinction between local and long range motion 

The relaxation studies in AFC illustrate how local and long range motions can be distinguished by careful measurements of different relaxation times. 

While according to the BPP model, the minimum in the T., vs. temperature plot is expected to occur at a lower temperature than that of the Ti minimum, in fact in AFC the behaviour is opposite as shown in Fig. 22.3. The minimum in appears to occur above room temperature while the minima of Ti occur well below 300 K. This clearly indicates that the two relaxation processes have different origins. It is concluded that while translational diffusion causes relaxation, it is the local reorientational dynamics that determines relaxation. 

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