Frequency characteristics of amplitude and phase of oscillating bubble systems in a closed measuring cell.

The amplitude- and phase-frequency characteristics of oscillating bubble systems with a closed measuring cell are analyzed. The shape of the frequency characteristics is qualitatively different for bubbles smaller or larger than a hemisphere, respectively, and also for diluted and concentrated surfactant solutions. Moreover, the presence of a surfactant in the solution strongly influences the characteristic frequencies of the system. The experiments performed under ground and microgravity conditions show a good qualitative agreement with theoretically predicted amplitude- and phase-frequency characteristics and confirm the adequacy of the proposed theory. The comparison of high-frequency limits of the surface dilatational elasticity with the theoretical Gibbs elasticities calculated according to the respective adsorption isotherm shows good agreement for small surfactant concentrations. At higher concentrations large discrepancies are observed which can possibly be explained by the violation of the linearity condition for the surface layer.