Photon correlation technique coefficient

The translational diffusion coefficient D is obtained from the first cumulant T of the electric field time correlation function (t), which is directly measured by photon correlation technique... 

Photon correlation spectroscopy (PCS) has been used extensively for the sizing of submicrometer particles and is now the accepted technique in most sizing determinations. PCS is based on the Brownian motion that colloidal particles undergo, where they are in constant, random motion due to the bombardment of solvent (or gas) molecules surrounding them. The time dependence of the fluctuations in intensity of scattered light from particles undergoing Brownian motion is a function of the size of the particles. Smaller particles move more rapidly than larger ones and the amount of movement is defined by the diffusion coefficient or translational diffusion coefficient, which can be related to size by the Stokes-Einstein equation, as described by... 

The expansion characteristics of carboxylic latex particles have been measured using three independent techniques sedimentation, which uses the change in particle density due to swelling to determine the change in particle size viscometry, which measures volume changes and photon correlation spectroscopy, which measures the diffusion coefficient of the particles. The sedimentation technique offers precise measurements at low shear but requires relatively... 

Diffusion coeffflcients can be readily measured by means of quasi-elastic or dynamic light scattering, also called photon correlation spectroscopy. For a description of the technique, we refer to sec. 1.7.8. In a dilute dispersion of spherical particles of bare radius a, the diffusion coefficient D can be directly related to d and a by the Stokes-Einsteln equation [1.6.3.321 ... 

A fundamental study was performed to demonstrate that flow FFF is a good alternative technique for the rapid measurement of protein diffusion coefficients [10]. The results obtained for 15 proteins were in good agreement (within 4%) with the literature data based on classical methods and a group of modern methods such as photon correlation spectrometry (PCS), laminar flow analysis, a chromatographic relaxation method, and analytical split-flow thin-cell (SPLITT) fractionation. The advantages of flow FFF are the high-speed separations and the calculation of D values directly from retention data. 

We now turn to a quantitative examination of the feasibility of conditional Fock state generation using our preparation and retrieval technique. For applications in long-distance quantum communication, the quality of the atomic state preparation is the most important quantity. Assuming perfect atom-photon correlations in the write Raman processes, we can find the density matrix p for the number of atomic spin-wave excitations conditioned on the detection of ns Stokes photons. Here we consider only the spin-wave modes correlated with our detection mode. For example, in the absence of losses and background, the conditional atomic density matrix is simply p(ns) = ns)(ns. Loss on the Stokes channel (characterized by transmission coefficient a.s) leads to a statistical mixture of spin-wave excitations,... 

To measure the droplet size distribution of the primary emulsion (W/O in W/O/W or O/W in O/W/O) that has a micron range (with an average radius of 0.5-1.0 pm), a dynamic light-scattering technique (also referred to as photon correlation spectroscopy PCS) can be apphed. Details of this method are described in Chapter 19. Basically, the intensity fluctuation of scattered light by the droplets as they undergo Brownian diffusion is measured from this, the diffusion coefficient of the droplets can be determined, and in turn the radius can be obtained by using the Stokes-Einstein equation. 

The thickness of the steric layers attached to colloidal particles can be measured by a variety of techniques viscometry (Doroszkowski and Lambourne, 1968 Fleer e/a/., 1972), sedimentation coefficient measurements (Garvey et ai, 1974), photon correlation spectroscopy (Garvey et al., 1976), surface balance measurements (Doroszkowski and Lambourne, 1971 1973), compression cell measurements (Cairns et al., 1976) and even electrophoretic measurements (Homola and Robertson, 1975). 

First, DLS measurements were conducted in the 1960s by analysing the intensity flucmations in terms of a frequency spectrum (frequency analysis— FA Cummins et al. 1964 Arrechi et al. 1967 Chu and Schones 1968 Dunning and Angus 1968). The width of the frequency spectrum is a measure of the relaxation time of the microstructural processes and can be employed for the determination of the particle diffusion coefficients (Pecora 1964). An alternative for evaluating the fluctuation of scattered light intensity is photon correlation spectroscopy (PCS), which has been used for the characterisation of colloidal suspensions since the end of the 1960s (lakeman and Pike 1969 lakeman 1970 Foord et al. 1970). PCS requires a different hardware than FA, but it can be shown that the results of both techniques are equivalent (lakeman 1970 Xu 2000, pp. 86-89). 

The most commonly used technique for determining 5 is photon correlation spectroscopy (PCS) [also known as quasi-elastic light scattering (QELS)]. PCS has become one of the standard tools of the trade for the colloid chemist. In this technique concentration fluctuations arising from the diffusive motion of the dispersion particles give rise to fluctuations in the dielectric constant of the medium are monitored photometrically. These fluctuations decay exponentially with a time constant related to the diffusion coefficient, Ds, of the scatterer, which can in turn be related to its hydrodynamic radius through the Stokes-Einstein equation ... 

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