Spin intrasegment

Later in the review we will distinguish intrasegment from intersegment dipolar couplings giving rise to two-proton spin-lattice relaxation contributions according to... 

Equations 63 and 64 are valid for intrasegment spin interactions. Since the Rouse model is experimentally relevant mainly for modes of relatively short chains or short chain sections, any contribution from intersegment dipolar interactions are neghgible on this time/frequency scale, and need not be treated expHcitly. 

Table 1. Theoretical dependences on time (f), angular frequency (co), and molecular mass (M) predicted by the tube/reptation model for the mean squared segment displacement and the intrasegment spin-lattice relaxation time in the four Doi/Edwards limits. The factors Q, Cj/, Qff, and Cr are frequency and molecular mass independent constants ...

Limit Mean squared segment displacement m= Refs Intrasegment spin-lattice relaxation time T intra 1 - Refs... 

These results should be asymptotically correct in the limit N oo and t 0.05(6 t)Vts For finite N, the exponents predicted in Eq. 132 may change slightly due to the stretched exponential decay of Cp t) given in Eq. 131. The limiting laws for the observables of interest in the frame of this review, the mean squared displacement and the (intrasegment) spin-lattice relaxation rate, are summarized in Table 2 (compare [49]). 

That is, dispersion region III is explained by the dominance of this intersegment contribution, whereas regions I and II are dominated by intrasegment spin interactions. 

Apart from these two relaxation dispersion regimes, which are mainly based on intrasegment spin interactions (and possibly nearest neighbor intersegment contributions), a third dispersion region specific for dipolar-coupled nuclei exists at low frequencies. This was shown to be due to (longdistance) dipolar interactions being relevant for protons but not for deuter-... 

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