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

Phys. Rev. Lett.

Mol, E. A. L, Wong, G. C. L, Petit, J. -M, Rieutord, F, & de Jeu, W. H. (1997). Thermal fluctuations of freely suspended smectic-A films from mesoscopic to molecular length scales. Phys.Rev.Lett., 79, 3439–3442.