Inelastic light scattering from the free surfaces of two nematic liquid crystals

Abstract

Laser light scattering and optical mixing spectroscopic techniques have been used to study the dispersion relation of kHz frequency thermally excited capillary waves on the free surfaces of p-azoxyanisole and p-azoxyphenetole. The experimentally determined dispersion relation agrees well with the predictions of hydrodynamic theory, both with respect to the frequency and to the damping of the waves.

The viscosities of nematic and smectic-A liquid crystals by inelastic light scattering

“…The experimental apparatus used here is very similar to that described earlier (McQueen 1973). Very briefly, light from a 15 mW He-Ne laser is reflected from the liquid crystal surface.…”

“…During recent years, inelastic laser light scattering from the free surfaces of nematic liquid crystals has been investigated both theoretically (Laagevin and Bouchiat 1972a) and experimentally (Langevin and Bouchiat 1972b, 1973, McQueen 1973. The surface tension and the three viscosities characteristic of the nematic mesophase can be obtained from the propagation frequency and the damping of the thermally excited capillary waves.…”

Scattering of Light on Surfactant-Laden Liquid-Liquid Crystal Interface

“…The theoretical description of surface waves at interfaces between nematic and isotropic liquids was first given by Langevin and Bouchiat (1972b) and successfully applied to investigate the properties of nematic-isotropic interfaces by surface light scattering (Langevin, 1972(Langevin, , 1975Bouchiat, 1972a, 1973;McQueen, 1973;McQueen and Singhal, 1974;Shih et al, 1983). Since then, several advances have been made in the study of capillary waves at nematic-isotropic interfaces (Parsons and Hayes, 1974;Hayes, 1975;Popa-Nita and Sluckin, 2002;Popa-Nita and Oswald, 2003;Popa-Nita et al, 2005;Elgeti and Schmid, 2005) that elucidate the role of the anisotropic structure of liquid crystal for the spectrum of surface waves.…”

Observation of high-speed nematic-to-crystal phase transition in p-azoxyphenetole

“…During some experiments on the free surface of p-azoxyphenetole (PAP) (McQueen 1973) it was noticed that if it was cooled slowly from the nematic phase towards the crystalline state a thin crystalline film suddenly appeared on its surface. The thickwalled brass container used was circular with a diameter of about 2.5 cm and 0.5 cm deep.…”