  The characterisation of the dynamic properties of viscoelastic monolayers of
surfactants at the gasliquid interface is very important in the analysis and
prediction of foam stability. With most of the relevant dynamic processes being
rapid (thermal fluctuation, film coalescence etc.) it is important to probe
interfacial dynamics at high deformation rates. Today, only few techniques
allow this, one of them being the characterisation of the propagation of
electrocapillary waves on the liquid surface. Traditionally, this technique has
been applied in a continuous mode (i.e. at constant frequency) in order to
ensure reliable accuracy. Here we explore the possibility to analyse the
propagation of an excited pulse in order to access the interfacial properties
in one single Fourier treatment over a wide range of frequencies. The main
advantage of this approach is that the measurement times and the required
liquid volumes can be reduced significantly. This occurs at the cost of
precision in the measurement, due partly to the presence of a pronounced
resonance of the liquid surface. The pulsed approach may therefore be used to
prescan the surface response before a more in-depth scan at constant frequency;
or to follow the changes of the interfacial properties during surfactant
adsorption.
