Original English dissertation · scientific equations reproduced directly from the source PDF.

3.2 Dynamic light scattering

Equation (3.26) allows to determine the half-with ΓR of Rayleigh-line from the correlation-time 1/2ΓR of the photon autocorrelation function.

• Photon statistics: All considerations have been done with the assumption that i(t) ∝ I(t). In principle, this can be done for sufficiently high scattering count rates. For experiments with lower rates it is substantial to use adequate statistics. This is described in detail in [46].

3.2.5 Technical equipment

A typical dynamic light scattering set-up is presented in Fig.(3.3). A frequency-doubled Nd:YAG laser (1) is used as light source. The laser light passes several diaphragms (2), a polarizer (4) and a collimator lens (5) with focal length f = 100 mm and is then fed to the sample cell (6). The scattered light passes a microscope objective (7), a polariza- tion analyzer (9) and the slit (10) with (d = 200 µm). Finally, the signal is detected by a photomultiplier (Hamamatsu Electronic, Model R647P) (12) that transforms a variation of intensity into a variation of voltage. The spectrometer is provided with a goniometer system which allow superior of scattering angle Θ. The received signal is analyzed with help of a correlation card ALV-5000/E with logarithmic timescale and with 288 channels. In principle it is possible to analyze the autocorrelation function in terms of a superposi- tion of up to four exponentials and thus four correlation times τc. Hence the Rayleigh line may be considered a sum of up to four Lorentz functions. Combining the correlation time τc with the Eqs.(3.1), (3.22) and (3.17) or (3.18), it is possible to determine the radius r of a particle and thus the correlation length ξ.

View original page 33 (authoritative equations, figures and layout)