Diffusing Wave Spectroscopy (ULUND)
Light Scattering
Description
The instrument is used for characterization of extremely turbid samples and is equipped with diode-pumped solid-state laser (wavelength of 660 nm) with a maximum power of 70 mW. The apparatus is implemented with a “Two-Cell Echo Technique” which allows reducing measurement times down to only a few minutes even for slowly relaxing and solid-like materials. The sample is filled into squared glass cells of 1 – 10 mm and placed in a temperature controlled sample environment (15-70ºC). The scattered light is detected with two efficient Avalanche Photo Diodes in transmission and processed by a multi-tau/linear correlator using pseudo-crosscorrelation as well as echo measurements. Also possible are experiments using backscattering geometry as well as CCD camera-based multispeckle measurements. The equipment runs with a powerful software solution (LS-Instruments, Fribourg, Switzerland) for data acquisition and analysis (combined correlation-echo measurements, single-, multi-speckle analysis, user defined multi-run scripts, online microrheology analysis and full data access).
The instrument is typically used for:
- Determination of mean square displacement (values as small as 1 nm measurable depending upon particle size)
- Determination of average particle size in concentrated suspensions.
- DWS-based microrheology
Possible instrument configuration
The instrument is implemented with the Two Cell and Two Cell Echo Technique, which allows for measurements of nonergodic samples and reduces measurement times to only a few minutes even for slowly relaxing and solid-like materials.
Local Contacts
- Dr. Peter Holmqvist
- Prof. Anna Stradner
