Q. What is infrared spectroscopy and what is it used for?
A. Infrared spectroscopy is a powerful tool for identifying an unknown substance, whether near, like a clue in a criminal investigation, or far. The Cassini mission to Saturn, for example, carries infrared spectroscopy equipment.
Infrared (literally "below the red") radiation has wavelengths between those of visible red light and microwaves; it is heat radiation, like what can be felt (but not seen) from the familiar infrared warming lamps.
Infrared spectroscopy reads the "fingerprint" of each chemical component of an unknown substance by bombarding it with this radiation and determining how much it absorbs and at which wavelengths. The resulting pattern, when read by a detector, is unique to that molecule or combination of molecules. The substance absorbs radiation at wavelengths that correspond to the energies of vibration of the various chemical bonds in the substance; the levels can be measured by a detector.
The resulting spectrum displays peaks that correspond to the wavelengths at which the substance has absorbed radiation. The magnitude of the absorption due to a certain substance is directly related to the concentration of that substance in the sample. The patterns also reflect the actual structure of the molecule being studied, with the unique twists, bends, rotations and vibrations of the chemical bonds between its atoms.
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