Diffusing-wave spectroscopy: Difference between revisions

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'''Diffusing-wave spectroscopy''' ('''DWS''') is an optical technique derived from [[dynamic light scattering]] (DLS) that studies the dynamics of scattered light in the limit of strong multiple scattering.<ref>

{{cite journal

|author1=G. Maret |author2=P. E. Wolf |year=1987

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<math>g_2(\tau)=\frac{\langle I(t)I(t+\tau)\rangle_t}{\langle I(t)\rangle_t^2}</math>

For the case of non-interacting particles suspended in a (complex) fluid a direct relation between g₂-1 and the [[mean squared displacement]] of the particles <Δr²> can be established. Let's us note P(s) the probability density function (PDF) of the photon path length s. The relation can be written as follows:<ref>

{{cite journal

|author=F. Scheffold

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}}</ref>

For quasi-transparent cells, an angle-independent variant method called Cavitycavity Amplifiedamplified Scatteringscattering Spectroscopyspectroscopy<ref>{{Cite journal |last1=Graciani |first1=Guillaume |last2=King |first2=John T. |last3=Amblard |first3=François |date=2022-08-30 |title=Cavity-Amplified Scattering Spectroscopy Reveals the Dynamics of Proteins and Nanoparticles in Quasi-transparent and Miniature Samples |url=https://pubs.acs.org/doi/10.1021/acsnano.2c06471 |journal=ACS Nano |volume=16 |issue=10 |language=en |pages=16796–16805 |doi=10.1021/acsnano.2c06471 |pmid=36039927 |arxiv=2111.09616 |s2cid=244345602 |issn=1936-0851}}</ref> makes use of an [[integrating sphere]] to isotropically probe samples from all directions, elongating photon paths through the sample in the process, allowing for the study of low turbidity samples under the DWS formalism.

==Multispeckle Diffusingdiffusing-Wavewave Spectroscopyspectroscopy (MSDWS)==

This technique either uses a camera to detect many speckle grains (see [[speckle pattern]]) or a ground glass to create a large number of speckle realizations (Echo-DWS <ref>{{Cite web|url=http://spie.org/x8591.xml?highlight=x2404&ArticleID=x8591|title=Light scattering technique reveals properties of soft solids}}</ref>). In both cases an average over a large number of statistically independent intensity values is obtained, allowing a much faster data acquisition time.

<gallery>

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<math>g_2(\tau)=\frac{\langle I(t)I(t+\tau)\rangle_p}{\langle I(t)\rangle_p^2}</math>

MSDWS is particularly adapted for the study of slow dynamics and non ergodic media. Echo-DWS allows seamless integration of MSDWS in a traditional DWS-scheme with superior [[temporal resolution]] down to 12&nbsp;ns.<ref>

{{cite journal

|author1=P. Zakharov |author2=F. Cardinaux |author3=F. Scheffold |year=2006

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==External links==

*[https://web.archive.org/web/20110930154856/http://www.formulaction.com/technology_dws.html Diffusing Wave Spectroscopy Overview with video]

*[http://www.lsinstruments.ch/technology/diffusing_wave_spectroscopy_dws/ Diffusing Wave Spectroscopy Overview with Animations] {{Webarchive|url=https://web.archive.org/web/20140520215951/http://www.lsinstruments.ch/technology/diffusing_wave_spectroscopy_dws |date=2014-05-20 }}

*[http://www.lsinstruments.ch/technology/diffusing_wave_spectroscopy_dws/dws_particle_sizing/ Particle Sizing using Diffusing Wave Spectroscopy] {{Webarchive|url=https://web.archive.org/web/20140520220247/http://www.lsinstruments.ch/technology/diffusing_wave_spectroscopy_dws/dws_particle_sizing/ |date=2014-05-20 }}

[[Category:Spectroscopy]]