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Chemistry LibreTexts

7: Vibrational Spectroscopy

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  • Another application of symmetry and group theory is in the interpretation of vibrational spectra, including both infrared spectra (IR) and Raman spectra. These spectroscopies measure the energies of molecular vibrations; but only the ones that either cause a change in the molecular dipole moment or a change in the molecular polarizability. Each vibrational mode has a symmetry represented in the character table of molecule's point group. When the symmetries of each vibrational mode are identified, we can predict how many vibrational bands we can expect in IR and Raman spectra. 

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