Fourier Transform Infrared (FTIR) spectroscopy is an analytical technique used to understand the structure of individual molecules and the composition of molecular mixtures. The fundamental vibrations of molecules occurs at the same frequency as infrared light. Molecules can absorb this light and convert it into molecular vibration. FTIR spectrometers allow us to monitor this absorption and as every molecule vibrates slightly differently, a unique infrared spectrum can be obtained.
The bands seen within a spectrum correspond to a particular vibration. Therefore, we can use the position (frequency) of these bands to identify specific molecular bonds. The intensity of the bands tells us how much light is absorbed, this is directly proportional to the number of bonds that are vibrating.