What is Infrared spectroscopy?
[[File:EM spectrum.svg|thumb|The electromagnetic spectrum showing infrared light next to the visible light.]] '''Infrared spectroscopy''' (sometimes called '''Infrared spectrometry''') is a physical [[analytical chemistry|analysis method]] that uses [[infrared]] [[light]]. Typically, infrared spectroscopy uses a [[wavelength]] between 800nm and 1mm. The method can be used for quantitative analyses of known substances, or of the structural properties of unknown substances. [[Raman spectroscopy]] is another method that produces similar results. The main method used in infrared spectroscopy today is [[Fourier transform infrared spectroscopy]], which uses [[Fourier transform]]s. Infrared vibrational spectroscopy can be used to identify [[molecules]] by listing their chemical bonds. An IR [[spectrometer]] is a [[machine]] that shines infrared light from a set range of frequencies on a sample. It measures which exact light frequencies are absorbed by the sample. [[Chemical bond]]<nowiki/>s in a molecule make [[molecular vibrations]] at frequencies that are characteristic of the bonds. A group of atoms in a molecule may have multiple modes of [[oscillation]] caused by the stretching and bending motions of the group as a whole. If an oscillation leads to a change in [[dipole]] in the molecule, then it will absorb a [[photon]] which has the same frequency. The vibrational frequencies of most molecules correspond to the frequencies of infrared light. Typically, the technique is used to study [[organic compound]]s using light radiation from 4000–400&nbsp;cm<sup>−1</sup>, the mid-infrared. The spectrometer records all the frequencies of absorption in a sample. This can be used to gain information about the sample composition in terms of chemical groups present and also its purity (for example a wet sample will show a broad O-H absorption around 3200&nbsp;cm<sup>−1</sup>). {{science-stub}} [[Category:Analytical chemistry]] [[Category:Physical chemistry]] [[Category:Infrared]]