Capillary wave analysis

We come to some important points in the analysis of capillary wave dynamics through the polar plot profile displayed in Fig. 4. First are the assumptions that we invoke in the analysis. Although the details will be better clarified when we come to the experimental part dealing with the SLS method, we must at this point lay down the assumptions and how they are in part justified. Throughout the entire scheme of capillary wave analysis presented here, we make the following assumptions ... 

Another approach to measurement of surface tension, density, and viscosity is the analysis of capillary waves or ripples whose properties are governed by surface tension rather than gravity. Space limitations prevent more than a summary presentation here readers are referred to several articles [123,124]. 

R. Evans. The role of capillary wave fluctuations in determining the liquid-vapor interface. Analysis of the van der Waals model. Mol Phys 42 1169-1196, 1981. 

In the past five years, it has been demonstrated that the QELS method is a versatile technique which can provide much information on interfacial molecular dynamics [3 9]. In this review, we intend to show interfacial behavior of molecules elucidated by the QELS method. In Section II, we present the principle and the experimental apparatus of the QELS along with the historical background. The dynamic collective behavior of molecules at liquid-liquid interfaces was first obtained by improving the time resolution of the QELS method. In Section III, we show the molecular collective behavior of surfactant molecules derived from the analysis of the time courses of capillary wave frequencies. Since the... 

The theoretical framework, within which the existence of surface instabilities created by capillary waves can be predicted is the linear stability analysis [23, 24]. This model assumes a spectrum of capillary waves with wave vectors q and time constant r (Fig. 1.8a). 

Stenvot C, Langevin D (1988) Study of viscoelasticity of monolayers using analysis of propagation of excited capillary waves. Langmuir 4 1179-1183... 

It may be of interest to note that Mandelstamm s analysis forms the basis of the capillary wave theory of surface tension. ... 

The equilibrium and dynamics of adsorption processes from micellar surfactant solutions are considered in Chapter 5. Different approaches (quasichemical and pseudophase) used to describe the micelle formation in equilibrium conditions are analysed. From this analysis relations are derived for the description of the micelle characteristics and equilibrium surface and interfacial tension of micellar solutions. Large attention is paid to the complicated problem, the micellation in surfactant mixtures. It is shown that in the transcritical concentration region the behaviour of surface tension can be quite diverse. The adsorption process in micellar systems is accompanied by the dissolution or formation of micelles. Therefore the kinetics of micelle formation and dissociation is analysed in detail. The considered models assume a fast process of monomer exchange and a slow variation of the micelle size. Examples of experimental dynamic surface tension and interface elasticity studies of micellar solutions are presented. It is shown that from these results one can conclude about the kinetics of dissociation of micelles. The problems and goals of capillary wave spectroscopy of micellar solutions are extensively discussed. This method is very efficient in the analysis of micellar systems, because the characteristic micellisation frequency is quite close to the frequency of capillary waves. 

More recently, Samec and coworkers investigated the line shape of the fluctuation spectrum at the polarizable water/DCE interface in the presence of the phospholipid DL-a-dipahnitoyl-phosphatidylcholine (DPPC) [32]. The line shape of experimental power spectra similar to those exemplified in Pig. 4.12 b was analyzed in terms of the mean vertical displacement of the interface generated by capillary waves. The experimental results in the presence and absence of DPPC at a wide potential range appear consistent with the description of the liquid/liquid boundary as molecularly sharjf. However it is not entirely clear from this analysis how sensitive the spectmm line shape is to the molecular organization at the liquid/Hquid boundary. As discussed in Section 4.3.2, vibrational sum frequency generation studies of the neat water/DCE interface provide a rather different conclusion. 

Since the neighbour slugs oscillate in phase opposition under shock load, pressure oscillations in the liquid plug should be restrained. Really the wave here turns out to be monotonous and its amplitude coincides practically with pressixre in the incident wave (Fig. 3). The applicability of Bq. (1) to the wave analysis is confirmed by experimental results ["l0. Fig.4 shows the comparison of these experiments conducted in a capillary horizontal tube ( 5 mm diam.) with air-water medium of slug structure, with the data of calculation by (1). 

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