Dynamics at the air-water interface revealed by evanescent wave light scattering

Abstract

Abstract.A new tool to study surface phenomena by evanescent wave light scattering is employed for an investigation of an aqueous surface through the water phase. When the angle of incidence passes the critical angle of total internal reflection, a high and narrow scattering peak is observed. It is discussed as an enhancement of scattering at critical angle illumination. Peak width and height are affected by the interfacial profile and the focusing of the beam. In addition, the propagation of capillary waves was studied at the surface of pure water and in the presence of latex particles and amphiphilic diblock copolymers. The range of the scattering vectors where propagating surface waves were detected is by far wider than standard surface quasi-elastic light scattering (SQELS) and comparable with those of X-ray photon correlation spectroscopy (XPCS).

Dynamics of amphiphilic diblock copolymers at the air–water interface

“…Sec. 2.5) shows for both block copolymers a different concentration behavior [33] comparing to surface pressure data. For PI 111 PEO 201 , I s decreases slightly at low concentrations passing through a shallow minimum at around 3 mg L −1 , before it increases significantly at high concentrations.…”

“…Recently we have described a new apparatus which implements multiple angle of incidence ellipsometry and evanescent light scattering together [32,33,34]. A cylindrical cell geometry is used, and allows ellipsometric scans from any incident angle ϕ above or below the interface being the incident beam always perpendicular to the cell's wall.…”

“…For liquid interfaces, this geometry was recently described by the authors, and experimental details can be found in the reference [33]. In this work, the light was always polarized in the direction parallel to the reflection plane (p-polarization).…”

“…In this work, the light was always polarized in the direction parallel to the reflection plane (p-polarization). Static scattered intensity I s was measured in a wide range 30 < ϕ(deg) < 70 of the incident angle, keeping the scattered angle ψ = 20 deg fixed [33].…”

Evanescent-wave dynamic light scattering at an oil-water interface: Diffusion of interface-adsorbed colloids

“…The apparatus described has been employed for highresolution ellipsometry on bare liquid-fluid interfaces [23] and the detection of capillary-wave dynamics [24].…”