Definition of vibrational spectroscopy

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Photonics Dictionary

vibrational spectroscopy: Vibrational spectroscopy is a type of spectroscopy that involves the study of the vibrational states of molecules. It is used to obtain information about the molecular structure, bonding, and environment by analyzing how molecules interact with electromagnetic radiation, typically in the infrared (IR) or Raman regions of the spectrum.

Energy levels: Vibrational spectroscopy probes the vibrational energy levels of molecules. These energy levels correspond to the various ways in which the atoms in a molecule can move relative to each other, such as stretching, bending, and twisting motions.

Infrared (IR) spectroscopy: In IR spectroscopy, molecules absorb infrared light at specific frequencies that correspond to the vibrational transitions. This absorption leads to a spectrum that is characteristic of the molecular structure and can be used to identify functional groups and chemical bonds.

Raman spectroscopy: In Raman spectroscopy, inelastic scattering of monochromatic light (usually from a laser) is measured. When light interacts with a molecule, it can scatter with a shift in energy corresponding to the vibrational energy levels of the molecule. This shift provides information similar to that obtained from IR spectroscopy but can be complementary, as different vibrational modes may be active in Raman versus IR spectroscopy.

Selection rules: The specific vibrational modes that are active in IR or Raman spectroscopy depend on the selection rules, which are determined by the changes in the dipole moment (for IR) or polarizability (for Raman) during vibration.

Vibrational spectroscopy is widely used in various fields, including:

Chemistry: For identifying chemical compounds and functional groups.

Materials science: To study the composition and properties of materials.

Biology: To investigate biomolecules like proteins, nucleic acids, and lipids.

Pharmaceuticals: For drug development and quality control.

Environmental science: To detect and analyze pollutants.