Fourier Transform Raman Spectroscopy (FT-Raman):
Principle : This technique is complementary to FT-IR and is a scattering technique, whereby a
laser beam (near-IR region) is directed to the sample and the scattered radiation is collected.
Most of the scattered radiation has the same wavenumber as that of the incident laser beam,
however a fraction will be having a different wavenumber. This is the Raman signal and
characteristic of particular functional group. Raman spectroscopy finds applications in
identifying organic compounds containing non-polar bonds such as carbon - carbon double
bonds or aromatic rings (weak dipoles).
Instrumentation : The instrumentation comprises of exciting laser normally in near-IR region,
Rayleigh filter, beam splitter, detector, etc. Data collection and processing are akin to IR
including the Fourier transformations.
Applications : The applications are similar to FT-IR and gives useful information on the non-
polar bonds, i.e. bonds with null or reduced dipole moment. Water is a good solvent for FT-
Raman.
Disadvantages : Signal strength is normally weak, and liquid samples give poor signals. Heat
sensitive samples can’t be analyzed, since local heating will damage the samples. Dark
colored samples can’t be analyzed.
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