Talk:Dynamic light scattering

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The introductory sentece says dynamic light scattering is also called "Photon Correlation Spectroscopy". I don´t get it: Where is the spectroscopy? --Maxus96 (talk) 18:20, 15 August 2009 (UTC)

As I vaguely remember, spectroscopy is very subtle here and there are several detection method. The most commercially viable is detecting infinitesimal shift in laser wavelength upon scattering on molecules, which is done by optical heterodyne detection. The photon correlation is also spectroscopy, but in the time-frequency domain (might be similar to FTIR spectroscopy). Sorry if this is too jargony. Materialscientist (talk) 23:18, 15 August 2009 (UTC)

It says that this is used in physics..? - But isn't that an understatement.. since this is used alot in chemistry as well..? —Preceding unsigned comment added by (talk) 11:05, 9 May 2010 (UTC)

The term Self Beat Spectroscopy was coined by Norman Ford and Photon Correlation Spectroscopy was coined by Pecora. The spectroscopic term relates to the interactions of the Photons at the point of detection. Self Beat Spectoscopy could also be added to the definition. Self-Beat Spectroscopy and Molecular Weight

AbstractHi-Res PDF[2739 KB]PDF w/ Links[2741 KB] N. C. FORD, JR., , R. GABLER, and , F. E. KARASZ University of Massachusetts, Amherst, Mass. 01002 Polymer Molecular Weight Methods Chapter 4, pp 25–54 Chapter DOI: 10.1021/ba-1973-0125.ch004 Advances in Chemistry, Vol. 125 ISBN13: 9780841201873eISBN: 9780841223066 Publication Date (Print): June 01, 1973 Copyright © 1973 —Preceding unsigned comment added by (talk) 20:21, 14 May 2011 (UTC)

Maximum entropy method[edit]

The text says "...reduce the χ2 of the fitted data". This requires further definition. Not only that, but I suspect that what is really minimized is the χ2 per fitted degree of freedom. Finally, the wikipedia maximum entropy page does not mention minimizing χ2, so it is unclear why this piece of information is on this page about DLS. — Preceding unsigned comment added by (talk) 18:08, 31 August 2012 (UTC)

The text on MEM is very unclear and basically incorrect. The MEM is based on the idea that there are, in effect, an infinite number of fits that can satisfy the inverse laplace transform in the presence of noise. The MEM attempts to select the solution that maximizes the entropy of the distribution in laplace space. That is, the distribution of exponential decay constants. with entropy defined as -∑p log p. The procedure replaces the χ2 maximization criterion with an entropy maximization criterion that is subject to the constraint that χ2 not exceed some statistically meaningful level. — Preceding unsigned comment added by (talk) 22:18, 11 February 2015 (UTC)

Incorrect explanation[edit]

The sentence 'The diffracted light from all of the molecules can either interfere constructively (light regions) or destructively (dark regions)' leads to a false idea, because it seems to make reference to the speckle pattern shown in the figure. There, the light regions are not regions where light arrives interfering constructively, but regions from which light interferes constructively at the retina/CCD of the camera. That's why primary speckle patterns depends on the position of the observer and seems to move in the opposite direction than the observer, when described by her/him/it.-- (talk) 09:01, 16 May 2016 (UTC)