Raman spectroscopy molecular symmetry effects

Polarization effects are another feature of Raman spectroscopy that improves the assignment of bands and enables the determination of molecular orientation. Analysis of the polarized and non-polarized bands of isotropic phases enables determination of the symmetry of the respective vibrations. For aligned molecules in crystals or at surfaces it is possible to measure the dependence of up to six independent Raman spectra on the polarization and direction of propagation of incident and scattered light relative to the molecular or crystal axes. 

Some of the carbyne complexes are particularly suitable for a precise determination of the chemical bonds. Their molecular and crystal structures possess high symmetry [1,2]. The molecules themselves are placed on high symmetrical sites in the crystal. In addition, big single crystals of some complexes can be obtained. These conditions are very favorable for electron deformation density studies and for other physical techniques such as polarised Raman spectroscopy in order to understand the nature of the chemical bonds existing in this class of compounds. It is also possible to compare these experimental results with ab iniV/o calculations. This paper relates some results of these studies, essentially focused on the conjugation effect of carbynes. 

Thus light of a particular frequency can simultaneously induce a dipole moment in a molecule and then couple with the dipole components to result in light absorption Raman spectra are observed within the spectram of light scattered from an intense source. Induced vibrational transitions are observed with a dispersive device (monochrometer) and some sort of electronic detection (in the visible range) at 9(f from the light source (laser) beam. Remarkably, C. V. Raman first observed this effect with a handheld spectroscope in 1928 for which he received the Nobel Prize in 1930. Thus we can examine the symmetry properties of second-order combinations of the Cartesian coordinates (in column 2 ) and use them to indicate a yes/no answer as to whether a given molecular vibration will occur in Raman spectroscopy. 

See also EPR, Methods Fluorescence Microscopy, Applications Fluorescent Molecular Probes Hole Burning Spectroscopy, Methods Laser Magnetic Resonance Laser Applications in Electronic Spectroscopy Laser Spectroscopy Theory Light Sources and Optics Luminescence Theory Near-IR Spectrometers Raman Optical Activity, Applications Symmetry in Spectroscopy, Effects of UV-Visible Absorption and Fluorescence Spectrometers Zeeman and Stark Methods in Spectroscopy, Applications. 

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