Abstract:

The scattering of a coherent light source, such as a laser, from any random medium invariably results in a far field scattering pattern consisting of light and dark regions, called a speckle pattern. If the scattering medium changes in time, as for example will happen if the scattering particles move, then the speckle pattern also changes in time, reflecting this motion. The analysis of the intensity fluctuations of a single speckle spot can provide information about the dynamics of the scattering medium, and this form of light scattering is called dynamic light scattering (DLS), or quasielastic light scattering. The traditional DLS experiment entails the measurement of the temporal autocorrelation function of the intensity fluctuations of a speckle spot, and for singly scattered light, the time constant of the decay of this correlation function can be related to the dynamics of the scattering system through knowledge of the scattering wave vector, q. This is a well developed form of light scattering spectroscopy, and traditional DLS has found many applications in the study of the dynamics of a wide variety of systems.

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