How to differentiate between mechanisms

In order to determine which relaxation mechanism is operating in a given case, you should rely on some estimates based on previous knowledge as well as doing experiments to sort out the different mechanisms. Using common sense and chemical knowledge, you can significantly narrow the number of possible mechanisms so that the correct experiments can be chosen. 

To estimate the strength of each interaction, you can rely on typical data for similar compounds from which extrapolation can be made. Lacking data on similar compounds, you can try to estimate the potential strengths of different mechanisms indirectly. 

Guessing at the relaxation mechanism will be easy when a general property of the sample makes it very likely for a single mechanism to dominate. Some examples would be metals in which the conduction electrons will be the source of relax- 

In the case of paramagnetic impurities, remember that the relaxation rate is usually proportional to the impurity concentration. Just to give you an idea, the T1 minimum for CaFg doped with lOOppm Gd at a flourine frequency of 20 

MHz is well under 100 ms (Fukushima and Uehling, 1968). Of course, in most situations, you will not be close to the T  

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