Characterization of order fluctuations in liquid crystals by the dipolar-correlation effect of the stimulated echo

Publisher Website
Google Scholar
Abstract
A NMR method is presented which permits one to probe order fluctuations in ordered materials such as nematics. Information on the order parameter is also accessible. The principle is based on the standard stimulated‐echo three‐pulse sequence. Both the stimulated and the primary echo are recorded. The quotient of the echo amplitudes is measured as a function of the spacing of the first two rf pulses. The attenuation curves of the quotient corrected for spin‐lattice relaxation show strong modulations directly reflecting the order parameter of the material. This dipolar‐correlation effect moreover provides information on the distribution of the director fluctuation modes. The time scale exceeds the millisecond range by far. A formalism has been developed which permits us the quantitative description of experimental data measured in nematic 5CB.