Study of the q divergence of nonequilibrium fluctuations in a stressed fluid

In this work we present some extremely low angle scattering data from a thermally stressed binary mixture. The sample is a thin layer of an aniline-cyclohexane mixture at the critical concentration stressed by a stable temperature gradient applied across the layer (heating from above). The theory predicts that the intensity scattered from nonequilibrium (n.e.) fluctuations should exhibit an impressive q−4 divergence. It is also predicted that gravity is the origin of a quench of the q divergence at extremely small scattering angles. Due to the unusually small scattering angles of the scattering setup, the divergence of the n.e. fluctuations can be established very clearly and, for the first time, we also present evidence of the gravity-induced quench at the smaller q vector range