FOURIER TRANSFORM INFRA-RED (FTIR) SPECTROMETER

FOURIER TRANSFORM INFRA-RED (FTIR) SPECTROMETER


An infrared spectrum presents a fingerprint of a sample with absorption peaks corresponding to the vibrations between the bonds of the atoms, constituting the material. Bonds in the molecules absorb infra red rays at one or more specific frequencies and produce vibrational characteristic of molecules in one of the three major parts of the infra red region, namely, Near Infrared (NIR), Mid Infrared (MIR) and Far Infrared (FIR). Organic compounds, H2O and CO2 may provide characteristic information in the Near to Mid Infrared region, while Far Infrared region display lattice vibrations, allowing identification of the mineral group (such as silicate, carbonate, sulfide, etc). However, this region is used only occasionally, as the molecules in minerals are too dense, and seldom display characteristic peaks, in routine measurement techniques. 

FTIR or Fourier Transform Infra Red spectrometer is the instrument which measures all of the infrared frequencies simultaneously with high sensitivity and at a great speed. A typical FTIR spectrometer consists:

1) optical bench or interferometer, which measures the intensity of a specially encoded IR beam after it has passed through a sample. The result signal called interferogram contains information about all frequencies present in it, and
2) mathematical program, where a computer reads the interferogram and uses Fourier Transform principle to decode IR information for each frequency and presents spectrum

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