Direct Nuclear-Magnetic-Resonance Measurements of Biaxiality in the Cholesteric Liquid Crystalline Phase

We report what we believe is the first experimental measurement of biaxiality in a cholesteric phase. This observation is made in a selectively deuterated nematic that was twisted by the addition of a chiral compound. A theoretically predicted biaxial order parameter (measured in terms of an asymmetry in the time-averaged deuterium quadrupole interaction) was found to be ∼${10}^{-3\mathrm{}}$ for a pitch ∼3 μm and to increase both with decreasing pitch and as the isotropic phase is approached.