Diffraction patterns from thin hexatic films

On the basis of a "spin-wave" analysis of coupled hexatic layers, we propose a form for the diffraction patterns from thin liquid-crystal films. We note that the deviations from "two-dimensional behavior" observed in recent experiments on films of a few layers can in fact be used to extract the effective hexatic Frank constant, and to probe its temperature dependence. Our predictions are found to be quite consistent with the experimental observations.