Infrared spectroscopy is a branch of spectroscopy which focuses on the infrared area of the electromagnetic spectrum. This area of the spectrum is found between the visible spectrum and the microwave spectrum. People are often aware of infrared radiation because it can produce heat, making it something which can be sensed even if it cannot be seen or heard, but it also has a number of other characteristics which make it of interest to people like chemists.
Spectroscopy in general is a discipline which involves learning more about the interaction between radiation and the objects it comes into contact with. One of the key tools in spectroscopy is a spectrometer, a device which can detect various wavelengths of energy. In the case of infrared spectroscopy, researchers are interested specifically in infrared radiation, and they use spectrometers which are calibrated to work with this kind of radiation.
In a simple example of how infrared spectroscopy might be used, a researcher or forensic technician might be confronted with an unknown substance. To learn more about the substance, a sample could be put into a spectrometer and subjected to infrared radiation to excite the molecules inside. Some of the radiation will be absorbed, which can be read by the spectrometer, and some will not, which can also be detected by the device. The device returns a printout showing how much radiation was absorbed, and which areas of the infrared spectrum were involved.
Classically, infrared spectroscopy results in a printout with a number of peaks at specific points. These peaks can be correlated with charts detailing the spectroscopy results of known substances. The researcher can see if there are any substances with similar infrared “signatures” to identify the unknown sample. Infrared spectroscopy can also be used to create a profile of a known material, to test for impurities and flaws by checking for tell-tale signs of signatures which do not belong, and so forth.
This type of work takes place in a lab equipped with a spectroscope and equipment which can be used to analyze the output. Many people use computer programs to visualize the spectroscopy results, as the computer results can be easily manipulated and studied. People can also compare other results with the use of overlays and compositing programs, an activity which many people may have seen on crime shows in which mystery substances are identified with the use of spectroscopy techniques.