Multi-Speckle Correlation Spectroscopy: Determining Sub-Ensemble and Time-Resolved Dynamics in Soft Matter
AIP Conf. Proc. 1518, 304 (2013), Soft Matter, 10, 5380 (2014)
Dynamic light scattering is the most popular technique for determining dynamic properties in soft matter. It enables one to monitor particle dynamics over an enormous time-interval of 11 decades. Ensemble-averaged dynamics in ergodic media can be determined using rather standard techniques. However, in non-ergodic samples (e.g. glasses) special experimental techniques are needed.
We have designed a new setup for multi-speckle dynamic light-scattering, which allows us to measure spatially-resolved autocorrelation functions of the scattered intensities. This is done to probe dynamics in spatially-separated sub-ensembles. Using well-designed detection optics, we detect the scattered light under a single scattering vector and image the scattering volume on a fast CCD-camera directly. The spatially-heterogeneous and ensemble-averaged dynamics can thus be measured. Time-resolved dynamics can be analyzed, as well.
MSCS reveals itself as a powerful tool in analyzing any colloidal sample of interest; specifically, in the temporal evolution of the ensemble-averaged intermediate scattering function and in the local particle dynamics. Dynamical heterogeneities in meta-stable colloidal samples can be made visible in great detail, which makes this an especially marked technique.
