Theory
Transmission Raman is possible because light scatters through turbid materials that do not significantly absorb or block the light. In a similar mechanism to Spatially Offset Raman Spectroscopy, the light in a diffusely scattering sample spreads through the object randomly (Transmission Raman can be regarded as an extreme example of SORS). As Raman photons can be created at all points that the light passes through the total scrambled Raman signal measured on the opposite face of the object is highly representative of the bulk of the material. This desirable property removes a problem with conventional, widely used back-scattering Raman spectroscopy where the signal tends to be representative of the surface and near-surface composition. Because Raman does not rely on absorption and the light spreads throughout the sample, a large thickness can be measured in the absence of photon absorption. This produces an analysis representative of the entire mixture and is typically insensitive to coatings, or thin containers.
Read more about this topic: Transmission Raman Spectroscopy
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