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An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups.
The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance (or transmittance ) on the vertical axis vs. frequency , wavenumber or wavelength on the horizontal ...
The first low-cost spectrophotometer capable of recording an infrared spectrum was the Perkin-Elmer Infracord produced in 1957. [3] This instrument covered the wavelength range from 2.5 μm to 15 μm (wavenumber range 4,000 cm −1 to 660 cm −1).
Researchers employ various organic and biochemical methods to introduce small vibrational probes into molecular systems into a variety of chemicals, proteins, nucleic acids, etc. [4] These probes, labeled with infrared (IR) markers, were subject to spectroscopic investigations to obtain quantitative insights into various features of chemical ...
The particle size should be smaller than the wavelength of the incident light in order to minimize Mie scattering, so this would infer that it should be less than 5 μm for mid-infrared spectroscopy. The spectra are plotted in units of log inverse reflectance (log 1/R) versus wavenumber.
The angular wavenumber may be expressed in the unit radian per meter (rad⋅m −1), or as above, since the radian is dimensionless. For electromagnetic radiation in vacuum, wavenumber is directly proportional to frequency and to photon energy. Because of this, wavenumbers are used as a convenient unit of energy in spectroscopy.
To use an IR spectrum table, first need to find the frequency or compound in the first column, depending on which type of chart that is being used. Then find the corresponding values for absorption, appearance and other attributes. The value for absorption is usually in cm −1. NOTE: NOT ALL FREQUENCIES HAVE A RELATED COMPOUND.
The infrared spectrum of liquid water is dominated by the intense absorption due to the fundamental O-H stretching vibrations. Because of the high intensity, very short path lengths, usually less than 50 μm, are needed to record the spectra of aqueous solutions.