Frequency dependence study of the proton spin relaxation in the re-entrant nematic phase

Proton T1 measurements are reported for two 60CB/80CB mixtures as functions of temperature and Larmor frequency. The frequency and temperature dependences of T1 support that different relaxation mechanism is responsible for spin relaxation in the nematic and in the re-entrant nematic phase. While the molecular self-diffusion is effective in the nematic phase, the orientational order director fluctuations play a dominant role in the re-entrant nematic phase.