OPTICAL STUDY OF THE MOLECULAR ALIGNMENT IN A NEMATIC LIQUID-CRYSTAL IN AN OBLIQUE MAGNETIC-FIELD

The light intensity I transmitted through a homeotropically oriented nematic liquid crystal slab held between crossed polarizers, as a function of the angle theta //H of an applied magnetic field, is calculated for oblique light incidence. The presence of singular points in the I vs. theta //H curve which are related to the elastic constants of the liquid crystal is demonstrated. The method turns out to be much more sensitive than the usual ones, mostly based on capacitance measurements and it is thus very suitable for determining the behavior of the elastic constants when the temperature is changed, particularly near the transition point.