| Popis: |
Quasi-elastic dynamic light scattering, better known as photon-correlation, is a preferred non-destructive technique to characterize colloidal suspensions and emulsions as to the size distribution of particles or droplets. We sketch the principle of measurement and indicate some of its limitations. These include the inability to work with highly concentrated suspensions where multiple scattering is significant, and the difficulty to deal simultaneously with relaxation times spanning several orders of magnitude such as they occur, e.g. in polymerizing solutions or in suspended biological matter. We describe system modifications which make it possible to eliminate these difficulties. A modified two-color optical setup together with cross-correlation permits the characterization of highly concentrated suspensions. A novel correlator layout permits the simultaneous evaluation of relaxation times over many orders of magnitude. |
