Quasi-elastic light Spectroscopy: photon

Photon Correlation Spectroscopy. Photon correlation spectroscopy (pcs), also commonly referred to as quasi-elastic light scattering (qels) or dynamic light scattering (dls), is a technique in which the size of submicrometer particles dispersed in a Hquid medium is deduced from the random movement caused by Brownian diffusion motion. This technique has been used for a wide variety of materials (60—62). [Pg.133]

The technique is alternatively called photon correlation spectroscopy (PCS) or quasi-elastic light scattering (QELS). [Pg.62]

Dynamic (quasi-elastic) light scattering that is usually referred as photon correlation spectroscopy this is a rapid technique that is especially suited to measuring submicron particles (nanosize range). [Pg.152]

Two scattering methods, namely time-average (static) Hght scattering and dynamic (quasi-elastic) light scattering (also referred to as photon correlation spectroscopy PCS), will be discussed in the following sections. [Pg.311]

DLS is a method that measures the time-dependent fluctuation of scattered intensity, and is also referred to as quasi-elastic light scattering or photon correlation spectroscopy. The latter term is the most commonly used for describing the process, since most dynamic scattering techniques employ autocorrelation. [Pg.415]

Polymeric materials were found in the toluene-insoluble fraction [127]. The materials have no solubility in common organic solvents or so-called fullerene solvents but are partially soluble in DMSO. Evidence for the polymeric nature of the materials includes results of dynamic scattering based on photon correlation spectroscopy of quasi-elastic light scattering (PCS-QELS) [128,129] and gel permeation chromatography using DMSO as mobile phase [117]. The structural characterization of the polymers remains a challenge. [Pg.370]

Dynamic light scallering (DLS). also known as photon correlation spectroscopy (I CS) and quasi-elastic light scattering (OFI.S). is a powerful technique for probing solution dynamics and fur measuring particle sues.-The DLS technique can obtain size information in a few minutes for particles with diameters ranging from a few nanometers to about 5 pm. [Pg.955]

This is also known as photon correlation spectroscopy (PCS) or quasi-elastic light scattering (QELS). It uses scattered light to measure the rate of diffusion of protein particles in a sample. The data on molecular motion are digitally processed to yield a size distribution of particles in the sample, where the size is given by the mean Stokes radius or hydrodynamic radius of the protein particles this is the effective radius of a particle in its hydrated state. Clearly, the hydrodynamic radius depends on both mass and shape. [Pg.139]

Ford NC. Theory and practice of photon correlation spectroscopy. In Dahneke BE, editor. Measurement of Suspended Particles by Quasi-elastic Light Scattering. New York WUey-Interscience 1983. p 31. [Pg.388]

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 ... [Pg.82]

Photon correlation spectroscopy — also dynamic light scattering (DLS) or quasi-elastic light scattering (QELS) — is a robust and rapid method for size determinations in the colloidal range (from about 5nm to 1 m ). In PCS, intensity fluctuations of the scattered light due to particle motion are measured in dependence on time. By the diffusion coefficient of the particles in the measurement fluid, the particle diameter can be calculated according the Stokes-Einstein Eq. (9.1) under the assumption of a spherical particle shape ... [Pg.404]

Dynamic light-scattering, also known as quasi-elastic light-scattering and photon correlation spectroscopy, makes use of scattering from very small... [Pg.101]

Dynamic light-scattering, sometimes called quasi-elastic light scattering or photon correlation spectroscopy, can be used to measure the diffusion coefficients of polymer chains in solution and colloids, a kind of Doppler effect see Section 3.6.6. In a dilute dispersion of spherical particles, the diffusion coefficient D is related to the particle radius, a, through the Stokes-Einstein equation. [Pg.657]

Measurement System Motions of polymer molecules in solution can be conveniently studied by using dynamic light scattering (DLS). It is also called quasi-elastic light scattering (QELS) and photon correlation spectroscopy... [Pg.168]

Dynamic light scattering involves the study of time-dependent fiuctuations in the intensity of scattered light which are the result of the Brownian motion of the particles. The random movement of the particles causes the distances between the particles to fiuctuate, causing constantly varying constructive and destructive interference patterns. This time-dependent fiuctuation in the intensity can be correlated with itself to obtain the diffusion coefficient of the particles. This method is also called photon correlation spectroscopy (PCS) and quasi-elastic light scattering (QELS) [21, 22]. [Pg.767]

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 ... [Pg.1154]

The theory and applications of the DLS method (which may also be referred to as quasi-elastic light scattering and photon[Pg.179]

A second ensemble technique is DLS (Nicoli et al, 1991) - also called quasi-elastic light scattering (QELS) or photon correlation spectroscopy (PCS) — which is based on analysis of the temporal fluctuations in the scattered intensity caused by Brownian motion, or diffusion, of the particles. In recent years, it has become a popular technique for characterizing many submicron colloidal systems, including polymer lattices, because of its large size range (roughly 1 nm to 5 p,m) and approximate independence from optical properties. [Pg.196]

In Table 2.1, PCS stands for photon correlation spectroscopy DWS for diffusing-wave spectroscopy QELS-SEF for quasi-elastic light scattering-... [Pg.60]