EQUILIBRATION IN A GRAVITATIONAL-FIELD NEAR THE CRITICAL CONSOLUTE POINT

The evolution of the concentration profile in a gravitational field ne ar the critical consolute point is studied by refractive index measure ments. The dependencies of the relaxation time on the distance to the critical level and temperature change are obtained. The decreasing of equilibration time for refractive index gradient is observed, while th e critical level is approached. This result contradicts with well-know n ''critical slowing down'' due to vanishing of diffusivity coefficien t at the critical consolute point. The proposed theoretical interpreta tion of this phenomena is based on key role of the critical layer with the highest concentration gradient and its width in gravitational fie ld. The decreasing of the width of critical layer results in speeding up of equilibration in the nearest vicinity of the critical point. The quantitative agreement of relaxation time dependencies with this theo retical analysis is found. (C) 1998 Elsevier Science B.V.