Nuclear relaxation due to contact coupling with unpaired electrons

5 NUCLEAR RELAXATION DUE TO CONTACT COUPLING WITH UNPAIRED ELECTRONS 

In the case of relaxation due to the contact term, the transition probabilities as defined in Fig. 3.8, where the splitting of the levels is now due to the contact contribution, are found to be 

This is because any scalar relaxation occurs through a flip-flop mechanism (Fig. 3.8)5  

Here the correlation time is x on of Eq. (3.7) and A is defined in Eq. (2.2). This differs from rc p of Eq. (3.6) because of the absence of the contribution from the rotational correlation time since the contact interaction, by its nature, is not 

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