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When the exciting laser energy corresponds to an actual electronic excitation of the molecule then the resonance Raman effect occurs. A classical physics based model is able to account for Raman scattering and predicts an increase in the intensity which scales with the fourth-power of the light frequency.
Therefore, the Raman spectrum (scattering intensity as a function of the frequency shifts) depends on the rovibronic states of the molecule. [7] The Raman effect is based on the interaction between the electron cloud of a sample and the external electric field of the monochromatic light, which can create an induced dipole moment within the ...
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 SERS effect is so pronounced because the field enhancement occurs twice. First, the field enhancement magnifies the intensity of incident light, which will excite the Raman modes of the molecule being studied, therefore increasing the signal of the Raman scattering. The Raman signal is then further magnified by the surface due to the same ...
Like ordinary Raman spectroscopy, RRS observes vibrational transitions producing a nonzero change in the polarizability of the molecule or material being studied. Resonance Raman scattering differs from fluorescence in that it occurs without vibrational relaxation during the lifetime of the excited electronic state.
Stimulated Raman spectroscopy, also referred to as stimulated Raman scattering (SRS), is a form of spectroscopy employed in physics, chemistry, biology, and other fields. . The basic mechanism resembles that of spontaneous Raman spectroscopy: a pump photon, of the angular frequency , which is scattered by a molecule has some small probability of inducing some vibrational (or rotational ...
[88] [89] Use of the English versions, "Raman effect" and "Raman lines" immediately followed. [90] [22] [91] In addition to being a new phenomenon itself, the Raman effect was one of the earliest proofs of the quantum nature of light. Robert W. Wood at the Johns Hopkins University was the first American to confirm the Raman effect in early 1929 ...
The basic principle of Raman optical activity is that there is interference between light waves scattered by the polarizability and optical activity tensors of a chiral molecule, which leads to a difference between the intensities of the right- and left-handed circularly polarised scattered beams.