Brillouin-scattering determination of the elastic constants of epitaxial fccC60film

Brillouin-light-scattering measurements have been performed on a (111) fcc film of ${\mathrm{C}}_{60}$ (fullerite) epitaxially grown on Ni(110). The Rayleigh surface wave has been detected for propagation along several directions on the film surface and shows an anisotropic behavior consistent with the (111) texture of the film. Bulk acoustic modes have also been measured. The Brillouin data allow the determination of the three independent elastic constants of fcc ${\mathrm{C}}_{60}$. The breakdown of the Cauchy condition indicates intermolecular interactions of non- central character.