Fourier-transform infrared spectroscopy
Fourier transform infrared spectroscopy (FTIR) is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gaseous material. An FTIR spectrometer collects high-resolution spectral data over a wide spectral range, from the near- to far-IR region.
Source: Wikipedia — Fourier-transform infrared spectroscopy (CC BY-SA 4.0)