Author(s): Avelino AlvarezOrdez, Miguel Prieto
Infrared (IR) spectroscopy studies the effect of interaction between matter and radiated energy in the IR range, and this effect is evaluated by measurement of the absorption of various IR frequencies by a sample situated in the path of an IR beam. When a beam of IR radiation is passed through a sample, the radiation can be either absorbed or transmitted, depending on its frequency and the structure of the molecules in the sample. IR radiation excites certain molecular groups, producing vibrations from the excited state at fixed wavelengths. The mechanical behavior of molecules is modified when energy quanta are supplied which change their vibrational and rotational modes. The absorption of energy occurs at frequencies corresponding to the molecular mode of vibration of the corresponding molecule or chemical group. As different functional groups absorb characteristic frequencies of IR radiation, the technique is used in sample identification and investigation of molecular structures.