Dynamic light scattering heterodyne

Fig. 17 Velocity profiles obtained using heterodyne dynamic light scattering for different mean shear rates along the flow curve 7= Is, 7= 5s, 7= 12s 7= 15s", 7= 22s" , and...

In dynamic light scattering experiments the motion of a particle with constant velocity results in a Doppler shift in the frequency spectrum. In a heterodyne experiment (mixing of a small portion of the unscattered light with the scattered one on the photomultiplier) this shift Aw can be directly determined from the power spectrum [98], providing the electrophoretic mobility by the simple relation... 

The literature [61,63-82] r rs to QELS by many differoit names, some of which are spediic methods of implemratation. The.se include dynamic light scattering, laser scattering, laser Doppler velocimeby, intensity fluctuation spectroscopy, photon correlation spectroscopy (PCS), light beating spectroscopy and homo- and heterodyne spectroscopy. Most of the techniques discussed here are based on PCS. 

Dynamic light scattering, photon correlation spectroscopy, heterodyne/ homodyne method) QELS Electromagnetic wave interaction 0,005-2... 

Bremer, L. G. B., Deriemaeker, L., Finsy, R., Gelade, E., Joosten, J. G. H., Fiber Optic Dynamic Light Scattering, neither Homodyne nor Heterodyne, Langmuir, 1993, 9, 2008-2014. 

The dynamics of the collective excitations can be determined conveniently by photon autocorrelation spectroscopy, which is also called self-beating, time-resolved Rayleigh or quasi-elastic light scattering spectroscopy [29]. Here the time autocorrelation function of the scattered light intensity G (t) is measured, which, in the heterodyne detection regime, is given by ... 

A typical measured autocorrelation function of the dynamically scattered light is shown in Fig. 4.5. It was obtained by using a nematic liquid crystal 4-n-pentyl-4 -cyanobiphenyl (5CB) and rubbed Nylon as aligning layer at a cell thickness of 2 qm [8]. The dots show the measured curve and the solid line the stretched exponential fit (4.20). The amplitude of the shows that the measurement was performed in a heterodyne regime as the intensity of the light scattered by fluctuations was fairly small. Therefore the characteristic... 

The longitudinal and transversal fluctuations of the shear modulus cause time correlation functions of the electric Held, which are measured by the heterodyne method (dynamic scattering of polarized and iinpolarized light) (see Kqiialion 2..S-32). 

---