Infrared Spectroscopy

Definition

Infrared spectroscopy is spectroscopy using infrared light (0.7–1000 μm; ∼14,000–10 cm⁻¹). Most molecular bonds are characterized by the absorption of specific frequencies of infrared radiation. The 0.7–2.5 μm (∼14,000–4000 cm⁻¹) region is often called the near-infrared, the 2.5–25 μm (4000–400 cm⁻¹) region is called the mid-infrared, and the 25–1000 μm (400–10 cm⁻¹) region is called the far-infrared.

Overview

Many organic and inorganic materials absorb unique frequencies of infrared light. The absorption is caused by vibrations or rotations of molecules, at frequencies corresponding to the infrared region of the electromagnetic spectrum. Therefore, information about molecular species and structure can be obtained by irradiating samples in the infrared frequency range and subsequently observing the absorption spectra or by observing the corresponding emission spectra if the intensities exceed that of the background radiation. Vibrational transitions in the infrared for some...