Rayleigh Linewidth Measurements on Binary Liquid Films near the Critical Point

The first measurements are reported of the Rayleigh linewidth of binary liquid films near the critical point for which the correlation length is comparable to the film thickness. The present data are in good agreement with the predictions of renormalization-group theory for binary liquids in three spatial dimensions with no adjustable fitting parameters. No influence of finite size or bounding surfaces on the linewidth are observed.