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Let us allow the scattering centers to move with a velocity v whose magnitude is much smaller than that of light in the medium that surrounds them. Due to the Doppler effect, the frequency, fs of the scattered light will differ from that of the incident light fi. The frequency difference, Δf, can be expressed as follows (for example, Zakian et al 2005, Chen et al 1997):
| Δf = [1 / (2π)] v q | (1) |
where q is the scattering vector.
Random movement of scattering centers, as in Brownian diffusion, does not cause a specific frequency shift but broadens the spectrum of scattered light in respect of the incident light spectrum. This broadening expresses itself in the time domain as an exponential decay of the irradiance auto-correlation function and is used in dynamic light scattering to measure the hydrodynamic particle size and the particle size distribution.
| CITATION: Jonasz M. 2006. Scattering vector and DLS (www.tpdsci.com/Tpc/ScaVctDLS.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 15-Jun-2006 Modified: 24-Aug-2006 Peer-reviewed: PENDING |
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