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Energy-level diagram showing the states involved in Raman spectra. Raman spectroscopy (/ ˈ r ɑː m ən /) (named after physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. [1]
The SPC file format is a file format in which all kinds of spectroscopic data, including among others infrared spectra, Raman spectra and UV/VIS spectra. The format can be regarded as a database with records of variable length and each record stores a different kind of data (instrumental information, information on one spectrum of a dataset ...
It states that no normal modes can be both Infrared and Raman active in a molecule that possesses a center of symmetry. This is a powerful application of group theory to vibrational spectroscopy, and allows one to easily detect the presence of this symmetry element by comparison of the IR and Raman spectra generated by the same molecule. [1]
The symmetry of a vibrational mode is deduced from the depolarization ratio ρ, which is the ratio of the Raman scattering with polarization orthogonal to the incident laser and the Raman scattering with the same polarization as the incident laser: = Here is the intensity of Raman scattering when the analyzer is rotated 90 degrees with respect ...
A Raman band whose depolarization ratio is less than 0.75 is called a polarized band, and a band with a depolarization ratio equal to or greater than 0.75 is called a depolarized band. [4] [5] For a spherical top molecule in which all three axes are equivalent, symmetric vibrations have Raman spectral bands which are completely polarized (ρ = 0).
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The spectrum of intensity differences recorded over a range of wavenumbers reveals information about chiral centres in the sample molecule. Raman optical activity can be observed in a number of forms, depending on the polarization of the incident and the scattered light.