Analysis of noises in photocurrent time‐correlation spectroscopy of scattered light

1976 ◽  
Vol 47 (2) ◽  
pp. 729-735 ◽  
Author(s):  
Kunitsugu Soda ◽  
Izumi Nishio ◽  
Akiyoshi Wada
Keyword(s):  
Scattered Light ◽  
Time Correlation ◽  
Correlation Spectroscopy

Scattered-light correlation spectroscopy of structural changes in aqueous systems

1992 ◽  
Vol 57 (1-2) ◽  
pp. 647-650
Author(s):  
M. V. Berezin ◽  
L. A. Dergacheva ◽  
L. V. Levshin ◽  
I. V. Mitin ◽  
A. M. Saletskii
Keyword(s):  
Structural Changes ◽  
Scattered Light ◽  
Correlation Spectroscopy ◽  
Aqueous Systems

scholarly journals On the use of two-time correlation functions for X-ray photon correlation spectroscopy data analysis

2017 ◽  
Vol 50 (2) ◽  
pp. 357-368 ◽  
Author(s):  
Oier Bikondoa
Keyword(s):  
Correlation Functions ◽  
Photon Correlation Spectroscopy ◽  
Time Correlation ◽  
Correlation Spectroscopy ◽  
Time Correlation Functions ◽  
Spectroscopy Data ◽  
Photon Correlation ◽  
X Ray ◽  
Equilibrium Processes ◽  
Time Correlations

Multi-time correlation functions are especially well suited to study non-equilibrium processes. In particular, two-time correlation functions are widely used in X-ray photon correlation experiments on systems out of equilibrium. One-time correlations are often extracted from two-time correlation functions at different sample ages. However, this way of analysing two-time correlation functions is not unique. Here, two methods to analyse two-time correlation functions are scrutinized, and three illustrative examples are used to discuss the implications for the evaluation of the correlation times and functional shape of the correlations.

scholarly journals Photon Correlation Spectroscopy Using Optical Heterodyne Detection

1981 ◽  
Vol 34 (5) ◽  
pp. 575 ◽  
Author(s):  
Guy C Fletcher ◽  
Julienne I Harnett
Keyword(s):  
Scattered Light ◽  
Local Oscillator ◽  
Correlation Spectroscopy ◽  
Polystyrene Latex ◽  
Heterodyne Detection ◽  
Experimental Comparison ◽  
Statistical Accuracy ◽  
Theoretical Predictions ◽  
Heterodyne Technique ◽  
Optical Heterodyne Detection

The detection by optical heterodyning of laser light scattered from solutions of macromolecules offers significant improvement in statistical accuracy over the more usual self-beating method. Nevertheless the heterodyne technique is not commonly used because of the supposed ifficulties associated with stable and efficient mixing of the scattered light with a local oscillator beam. We have carried out an experimental comparison of several methods of mixing the two beams, using very dilute solutions of polystyrene latex spheres as scatterers. Experimental data are also presented for the apparent particle radius as a function of the local oscillator level, and are compared with theoretical predictions.

Sequential Extraction of Late Exponentials (SELE): A technique for deconvolving multimodal correlation curves in Dynamic Light Scattering

MRS Advances ◽  
2020 ◽  
Vol 5 (17) ◽  
pp. 865-880 ◽  
Author(s):  
Preethi L Chandran
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Sequential Extraction ◽  
Time Scales ◽  
Scattered Light ◽  
Correlation Spectroscopy ◽  
Least Square ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Correlation Curve

Abstract:In techniques such as Dynamic Light Scattering (DLS), Fluorescence Correlation Spectroscopy, and image mining, motion is tracked by the autocorrelation of a signal over logarithmic time scales. For instance the tracking signal in DLS is the scattered light intensity; it remains correlated at time scales where scant changes in the arrangement of the scattering particles occur, but decays exponentially at the time scales of their diffusion. When there are multiple time scales of motion (for instance due to scatterers of different sizes), the correlation curve has more than one exponential fall. Extracting the decay constants or hydrodynamic sizes due to each exponential fall in a multi-species field correlation curve becomes an ill-conditioned mathematical problem. We describe a new algorithm to invert a multi-modal correlation curve by Sequential Extraction of the Late Exponentials (SELE). The idea is that while the inversion of a multi-exponential equation may be ill posed, that of a single exponential is not. So we fit data windows towards to base of the correlation curve to extract the largest contribution species, remove the species contribution from the correlation curve, and repeat the process with the remnant curve. The single exponent can be robustly fitted by least-square minimization with initial guesses generated by an adapted cumutant technique (power-series) that includes stretch coefficients (measure of sample dispersity). The proposed algorithm resolves particle sizes separated by 3X, and is reliable against fluctuations in the correlation curve and to localized regions of suboptimal data. The algorithm can be used to track particle dynamics in solution in multi-species problems such as self-assembly.

Dynamics of Buried Polymer -polymer Interfaces in Thin Films

2003 ◽  
Vol 790 ◽  
Author(s):  
L. B. Lurio ◽  
Xuesong Hu ◽  
Suresh Narayanan ◽  
Xuesong Jiao ◽  
Jyotsana Lal
Keyword(s):  
Standing Wave ◽  
Diffuse Scattering ◽  
Grazing Incidence ◽  
Time Correlation ◽  
Correlation Spectroscopy ◽  
Polymer Interface ◽  
A Value ◽  
Vacuum Interface ◽  
Measured Time ◽  
Set Up

ABSTRACTWe have performed x-ray photon correlation spectroscopy (XPCS) measurements on a polymer-bilayer system comprised of 100 nm polystyrene film on top of an 80 nm polybromostyrene film, supported on a Si substrate. In order to distinguish the dynamics at the top interface from that at the polymer-polymer interface we have performed the measurement at grazing incidence. In this geometry, a standing wave is set up in the film. We derive a relation for the intensity of the standing wave and the resulting diffuse scattering. This model is compared with the measured diffuse scattering from which we extract a value of 0.7±0.4 dyne/cm for the surface tension between PS and PBrS at 180C. XPCS was then measured in each of two standing wave conditions, first where diffuse scattering only occurs at the polymer-vacuum interface and then where it only occurs at the interior polymer-polymer interface. The measured time correlation functions for each of the two interfaces show clear differences, with the polymer-polymer interface exhibiting much slower dynamics.

scholarly journals Non-equilibrium processes in martensitic phase transformations by X-ray photon correlation spectroscopy

2015 ◽  
Vol 1754 ◽  
pp. 141-146
Author(s):  
Michael Widera ◽  
Uwe Klemradt
Keyword(s):  
Photon Correlation Spectroscopy ◽  
Time Correlation ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Equilibrium Dynamics ◽  
Speckle Patterns ◽  
Martensitic Phase Transformations ◽  
Non Equilibrium

ABSTRACTThrough undulator sources at 3rd generation synchrotrons, highly coherent X-rays with sufficient flux are nowadays routinely available, which allow carrying over photon correlation spectroscopy (PCS) from visible light to the X-ray regime. X-ray photon correlation spectroscopy (XPCS) is based on the auto-correlation of X-ray speckle patterns during the temporal evolution of a material and provides access both to equilibrium and non-equilibrium properties of materials at the Angstrom scale. Owing to technical limitations (detector readout), XPCS has typically been used for the detection of slow dynamics on the scale of seconds. The variety of scattering geometries employed in conventional X-ray analysis can be combined with XPCS. In this work, we report on bulk diffraction (XRD) used to study the prototypical shape memory alloy Ni63Al37 undergoing a structural, diffusionless (martensitic) transformation. Two-time correlation functions reveal non-equilibrium dynamics superimposed with microstructural avalanches.

scholarly journals A Comprehensive Review of Fluorescence Correlation Spectroscopy

2021 ◽  
Vol 9 ◽  
Author(s):  
Lan Yu ◽  
Yunze Lei ◽  
Ying Ma ◽  
Min Liu ◽  
Juanjuan Zheng ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Fluorescence Correlation Spectroscopy ◽  
Pair Correlation ◽  
Time Correlation ◽  
Correlation Spectroscopy ◽  
Local Concentration ◽  
Fluorescence Correlation ◽  
Pros And Cons

Fluorescence correlation spectroscopy (FCS) is a powerful technique for quantification of molecular dynamics, and it has been widely applied in diverse fields, e.g., biomedicine, biophysics, and chemistry. By time-correlation of the fluorescence fluctuations induced by molecules diffusing through a focused light, FCS can quantitatively evaluate the concentration, diffusion coefficient, and interaction of the molecules in vitro or in vivo. In this review, the basic principle and implementation of FCS are introduced. Then, the advances of FCS variants are reviewed, covering dual-color FCCS, multi-focus FCS, pair correlation function (pCF), scanning FCS, focus-reduced FCS, SPIM-FCS, and inverse-FCS. Besides, the applications of FCS are demonstrated with the measurement of local concentration, hydrodynamic radius, diffusion coefficient, and the interaction of different molecules. Lastly, a discussion is given by summarizing the pros and cons of different FCS techniques, as well as the outlooks and perspectives of FCS.

Calibration of Probe Volume in Fluorescence Correlation Spectroscopy

2007 ◽  
Vol 61 (9) ◽  
pp. 956-962 ◽  
Author(s):  
Yi Gao ◽  
Zhenming Zhong ◽  
M. Lei Geng
Keyword(s):  
Correlation Functions ◽  
Fluorescence Correlation Spectroscopy ◽  
Time Correlation ◽  
Correlation Spectroscopy ◽  
Beam Radius ◽  
Data Sets ◽  
Probe Volume ◽  
Calibration Process ◽  
Fluorescence Correlation ◽  
Dimensional Parameters

In fluorescence correlation spectroscopy (FCS), an accurate evaluation of the probe volume is the basis of correct interpretation of experimental data and solution of an appropriate diffusion model. Poor fitting convergence has been a problem in the determination of the dimensional parameters, the beam radius, ω, and the distance along the optical axis of the probe volume, l. In this work, the instability of fitting during the calibration process is investigated by examining the χ2 surfaces. We demonstrate that the minimum of χ2 in the ω dimension is well defined for both converging and diverging data. The difficulty of fitting comes from the l dimension. The uncertainty in l could be significantly larger than that in ω, as determined by F-statistics. A modified calibration process is recommended based on examining two data treatment methods, combining several short data sets into a single long run and averaging the correlation functions of several short data sets. It is found that by using the mean of several converging correlation functions from short data sets instead of a long time correlation, more stable and consistent dimensional parameters are extracted to define the probe volume.

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