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Absorption peak (cm −1) Appearance C─H alkyl methyl 1260 strong 1380 weak 2870 medium to strong 2960 medium to strong methylene: 1470 strong 2850 medium to strong 2925 medium to strong methine: 2890 weak vinyl: C═CH 2: 900 strong 2975 medium 3080 medium C═CH 3020 medium monosubstituted alkenes: 900 strong 990 strong cis-disubstituted ...
The central peak is at the ZPD position ("zero path difference" or zero retardation), where the maximal amount of light passes through the interferometer to the detector. The goal of absorption spectroscopy techniques (FTIR, ultraviolet-visible ("UV-vis") spectroscopy , etc.) is to measure how much light a sample absorbs at each wavelength. [ 2 ]
The intrinsic physicochemical property of each particular molecule determines its corresponding IR absorbance peak, and therefore can provide characteristic fingerprints of functional groups (e.g. C-H, O-H, C=O, etc.). [1] In geosciences research, FTIR is applied extensively in the following applications:
The linear absorption (FTIR) spectrum is indicated above the 2D IR spectrum. The two peaks in the 1D spectrum reveal no information on coupling between the two states. After the waiting time in the experiment, it is possible to reach double excited states. This results in the appearance of an overtone peak.
The peak at the center is the ZPD position ("zero path difference"): Here, all the light passes through the interferometer because its two arms have equal length. The method of Fourier-transform spectroscopy can also be used for absorption spectroscopy. The primary example is "FTIR Spectroscopy", a common technique in chemistry.
A common spectroscopic method for analysis is Fourier transform infrared spectroscopy (FTIR), where chemical bonds can be detected through their characteristic infrared absorption frequencies or wavelengths. These absorption characteristics make infrared analyzers an invaluable tool in geoscience, environmental science, and atmospheric science.
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The dispersive method is more common in UV-Vis spectroscopy, but is less practical in the infrared than the FTIR method. One reason that FTIR is favored is called "Fellgett's advantage" or the "multiplex advantage": The information at all frequencies is collected simultaneously, improving both speed and signal-to-noise ratio.