Order Parameter Fluctuations in the Nematic Phase

Just below Tc, fluctuations in the magnitude of the nematic order parameter S may be studied by NMR spin relaxation. In particular, if these order parameter fluctuations (OPF) are dominant in comparison with the director fluctuations, then 1/Tidf in Eq. (6.62) is replaced by 1/Tioi , which has been discussed by Freed [6.9]. In fact, the modifications to the spectral density given in Eq. (6.91) are slight, i.e.. 

The proton was found to increase in the nematic phase of PAA-dg as Tc was approached [6.70]. This has been interpreted as due to the critical behavior of in Eq. (6.97). The interpretation is complicated, however, by other relaxation contributions. 

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