page_title: Geology applications of Fourier transform infrared spectroscopy
section_title: Instrumentation
hierarchical_section_title: Geology applications of Fourier transform infrared spectroscopy / Instrumentation
caption_attribution_description: English: Interferometer for FTIR
context_page_description: Fourier transform infrared spectroscopy is a spectroscopic technique that has been used for analyzing the fundamental molecular structure of geological samples in recent decades. As in other infrared spectroscopy, the molecules in the sample are excited to a higher energy state due to the absorption of infrared radiation emitted from the IR source in the instrument, which results in vibrations of molecular bonds. The intrinsic physicochemical property of each particular molecule determines its corresponding IR absorbance peak, and therefore can provide characteristic fingerprints of functional groups.
  In geosciences research, FTIR is applied extensively in the following applications:
  Analysing the trace amount of water content in Nominally anhydrous minerals
  Measuring volatile inclusions in glass and minerals
  Estimating the explosion potential in volcanic setting.
  Analysing chemotaxonomy of early life on earth
  Linking biological affinities of both microfossils and macrofossils
  These applications are discussed in details in the later sections. Most of the geology applications of FTIR focus on the mid-infrared range, which is approximately 4000 to 400 cm⁻¹.
context_section_description: The fundamental components of a Fourier transform spectrometer include a polychromatic light source and a Michelson Interferometer with a movable mirror. When light goes into the interferometer, it is separated into two beams. 50% of the light reaches the static mirror and the other half reaches the movable mirror. The two light beams reflect from the mirrors and  combine as a single beam again at the beam splitter. The combined beam travels through the sample and is finally collected by the detector. The retardation (total path difference) of the light beams between the static mirror and the movable mirror results in interference patterns. The IR absorption by the sample occurs at many frequencies and the resulting infereogram is composed of all frequencies except for those absorbed. A mathematical approach Fourier Transform converts the raw data into spectrum.
caption: The basic components of a Michelson Interferometer: a coherent light source, a detector, a beam splitter, a stationary mirror and a movable mirror.
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