0000000000230284
AUTHOR
Jürgen Dr. Müller
Probing slow fluctuations in nonergodic systems: Interleaved sampling technique
We present a new dynamic light scattering scheme to obtain ensemble-averaged correlation functions of slow fluctuations in non-ergodic systems in an efficient way. On a rotating sample, a large set of separate correlation functions is measured in parallel, for each independent orientational component of the sample’ density fluctuations. The ensemble-averaged correlation function spans a lag time range from 1 to 104 s. We describe our first implementation of this technique, discuss its statistical accuracy and show first results. Compared to plain ensemble averaging over a series of N measurements, the total measurement time is usualy reduced by a factor N without significant degradation of …
High-resolution particle sizing by optical tracking of single colloidal particles
Abstract The motion of individual Brownian particles is observed using the confocal Tracking Microscope recently introduced by Schatzel (K. Schatzel, W. G. Neumann, J. Muller and B. Materzok, App. Opt. 31 (1992) 770–778). Particles are laterally trapped in a strongly focused laser beam. By evaluating the light-pressure-induced drift velocity and the backscattered intensity we are able to detemine particle size histograms with a resolution better than 2%. This is demonstrated on a mixture of seven species of polystyrene latex spheres in the diameter range between 300 and 450 nm, where six classes of diameters are identified. We discuss the scope of the method and potential applications.