Intramolecular character of the intrapair dipolar order relaxation in the methyl deuterated nematic para-azoxyanisole

The proton intra-pair dipolar order relaxation time (T1D) was measured for nematic methyl-deuterated para-azoxyanisole (PAAd6) as a function of both the temperature and concentration in perdeuterated PAA (PAAd14), at 27 MHz. Since the results coincide for all measured concentrations in all the nematic temperature range, we conclude that the intermolecular contribution to the relaxation of the dipolar energy in this compound is negligible, at the studied frequency. The observed temperature dependence of T1D is typical of the order fluctuations of the director (ODF), which clearly indicates that the ODF is the relevant mechanism producing dipolar order relaxation, in accordance with previous field cycling experiments.