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Photothermal deflection spectroscopy

Photothermal Deflection Spectroscopy is a kind of spectroscopy that measures the change in refractive index due to laser heating of a surface. It works via the mirage effect where a refractive index gradient exists adjacent to the substrate's surface. The test laser beam is diffracted or bent in a manner proportional to the temperature of the surface. From this the ratio of absorption over scattering can be determined.

It is of particular value in situations where "pass through" or transmission spectroscopy can't be used.

Typically the surface is heated using a pulsed light source. A lock-in amplifier is then used to measure deflections found at this frequency.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Photothermal_deflection_spectroscopy". A list of authors is available in Wikipedia.
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