Interpretation of the Nuclear Spin-Lattice Relaxation-Time Behavior in the Nematic Mesophases

We give a coherent quantitative interpretation of both the frequency and temperature behavior of the proton spin-lattice relaxation time T₁ in the nematic phase of p-azoxyanisole. The frequency dependence of T₁ is dominated by the long-wavelength thermal fluctuations in the orientational order. The temperature dependence of T₁ has an important contribution from short-range phenomena involved in the motion of methyl protons. The activation energy for this motion is W≈9 kcal/mole.