Evanescent Wave Dynamic Light Scattering (FZJ - ICS3)
Light Scattering
Description
Evanescent Wave Dynamic Light Scattering (EWDLS) is a versatile method to study the motion of colloidal particles at solid-liquid interface. The instrument consists of three units: an incident units, a flexible sample stage and a detecting unit.
The basic principle is such: when the laser beam shoots at the glass-solution interface under total reflection, an inhomogenous evanescent field is created close to the interface, which is used as illumination source; particles within the illumination field scatters light, and the scattered light is collected by the detecting unit and passed down to the correlator; a correlation function is then generated, from which we obtain the information on particle dynamics.
The penetration depth of evanescent wave can be tuned by varying the incident angle of laser beam. Thanks to the two degrees of freedom in detecting unit, the instrument can distinguish the anistropic motion of particles parallel and pependicular to the interface.
The sample stage is rather flexible. At the moment, we have two types of stages: a stationary one and a shear cell. The former enables users to measure particle dynamics at equilibrium stage, while the latter makes it possible to study particle dynamics under shear flow.
The specification of the instrument is listed below.
- Laser wavelength and power: 150 mW at 532 nm;
- Range of particle diameter: 100 nm to 1000 nm;
- Refractiv index of the glass lens : 1.736 ;
- Penetration depth: 100 nm <\kappa^{-1}<800 nm
- Accessible scattering vector Q:
- Angular resolution: <1 degree
- Shortest relaxation time accessible: 10-5 s
- Polarization: available
Local Contacts
- Prof. Peter Lang
- Dr. Yi Liu
