CONFINEMENT EFFECTS ON THE COLLECTIVE EXCITATIONS IN THIN NEMATIC FILMS

The influence af confinement on the spectrum of collective excitations in ultrathin nematic layers of octylcyanobiphenyl is studied, using q uasielastic light scattering in planarly and hybridly aligned films, B oth systems show confinement-induced relaxation rate gaps in the origi nally gapless spectrum of director fluctuations, On the mesoscopic sca le, the magnitude of the relaxation rare gap scales as the inverse thi ckness of the nematic layer and can be very well described by a Landau -de Gennes theory, in which the boundary conditions play an important role.