Using surface laser light scattering spectroscopy, we have observed for the first time the crossover from capillary to Rayleigh (elastic) surface fluctuations on polymer solutions. At low polymer concentrations c<${\mathit{c}}^{\mathrm{*}}$ solutions of polyisobutylene in hexane exhibit ordinary capillary waves on the free surface; at higher concentrations, c>${\mathit{c}}^{\mathrm{*}}$ the capillary mode evolves into a Rayleigh mode. The surface laser light scattering data is quantitatively discussed within the context of recent theory.

• Received 15 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.2439