CHARACTERISTICS OF THE CAPILLARY MOTIONS OF SURFACTANT SOLUTIONS WITHA CHARGED FREE-SURFACE

A dispersion relation is derived and analyzed for the spectrum of capi llary motions on the charged plane surface of a liquid in which a surf actant is dissolved. It is shown that two additional wave motions are generated in this kind of system by bulk diffusion and surface diffusi on of the surfactant and are sensitive to the diffusion coefficients a nd elastic properties of the surfactant films and to the viscosity of the solution and the presence of a surface charge. In solutions of ina ctive surfactants the growth rate of Tonks-Frenkel instability increas es as the surfactant concentration increases. (C) 1998 American Instit ute of Physics. [S1063-7842(98)00502-9].