Concentration fluctuations of a binary liquid mixture in a macroporous glass

We performed static and dynamic light scattering measurements for the binary liquid mixture, carbon disulfide–nitromethane, imbedded in a 1000-Å porous glass. The system exhibits strong spatial but weak temporal fluctuations, giving rise to interesting nonergodic behavior. A reasonably sharp transition was detected at a temperature ∼1 K below the bulk ${\mathit{T}}_{\mathit{C}}$, with the system showing critical slowing-down on both sides of the transition. Despite the large pore size (in comparison with the correlation length), the intensity-intensity autocorrelation function is nonexponential with a characteristic relaxation time that does not diverge even at low temperatures, T≪${\mathit{T}}_{\mathit{C}}$. Our observations cannot be explained by the random-field model.