THERMAL FLUCTUATIONS OF FREELY SUSPENDED SMECTIC-A FILMS FROM MESOSCOPIC TO MOLECULAR LENGTH SCALES

The thermal fluctuations of freely suspended smectic-A films have been studied with diffuse x-ray scattering. Using a (2 + 2) scattering geo metry at a synchrotron source the spectral dependence of the displacem ent-displacement correlation function has been determined from mesosco pic to molecular dimensions. At long in-plane length scales the fluctu ations of the smectic layers were found to be conformal; i.e., all lay ers of the film fluctuated in unison. At decreasing length scales conf ormality was progressively lost, starting between the top and bottom l ayers of the film.