A study of kinetic molecular exchange processes in the medium frequency range by surface SHG on an oscillating bubble [Elektronisk resurs]

• The dilatational properties of fluid surfaces and interfaces have been comprehensively investigated in recent years. For example, an im-proved oscillating bubble device provided experimental results that allow for critical testing of established surface models, such as theLucassen/van den Tempel (LvdT) model. The comparison of the LvdT model with the oscillating bubble experiments demonstrates a mis-match between the model parameters. For example, near the CMC or the limit of solubility the calculated parameters of surfactant solutionsbecome unrealistically large. The deviation can be explained by the introduction of more detailed surface models, in particular by the mod-ification of the effective thickness of the surface layer, its internal structure and the molecular exchange processes between these structures.For the verification of such processes an experimental setup was realized which allows for an independent determination of the instanta-neous adsorption state at the surface of an oscillating bubble inside a surfactant solution. The setup utilizes the Second Harmonic Generation(SHG)—effect at the air–solution interface generated by the light of a pulsed LASER. The set-up is described in detail, and the results of afirst experimental series are presented and discussed in this paper. As system, aqueous solutions of the fluortenside F381 were used. 

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