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Fourier transform infrared spectrometer, also called Fourier transform infrared spectrometer, conforms to the principle of dispersion infrared spectroscopy, is an infrared spectrometer developed based on the principle of Fourier transform of infrared light after interference.
Mainly composed of infrared light source, diaphragm, interferometer (beam splitter, movable mirror, fixed mirror), sample chamber, detector and various infrared reflectors, lasers, control board and power supply. It can perform qualitative and quantitative analysis on samples, and is widely used in the fields of medicine, chemical industry, geology and mining, petroleum, coal, environmental protection, customs, gemstone identification, criminal investigation and identification, etc.
Working principle:
Infrared rays are electromagnetic waves like visible light, and infrared rays are electromagneticical waves with a wavelength between visible light and microwaves.
Infrared light can be divided into three wavelength ranges depending on the wavelength range: near infrared, middle infrared and far infrared. It is most effective to solve various problems in molecular structure and chemical composition, so the mid-infrared range is the most commonly used range in infrared spectroscopy, commonly known as Infrared spectrum mostly refers to this range.
The infrared spectrum belongs to the absorption spectrum, which is caused by the absorption of infrared light of a specific wavelength when the compound molecule vibrates. The wavelength of infrared light absorbed by vibration of chemical bond depends on chemical bond kinetic constant and compound atomic equivalent mass at both ends so depends on structural features. This is the theoryical basis for determining the structure of compounds using infrared spectroscopy.
Infrared spectroscopy as a molecular fingerprint is often used to investigate the molecular structure and chemical composition of substances.
According to the position, intensity and shape of the band frequency obtained after the molecule absorbs infrared light and the relationship between the absorption band and the temperature, state of matter, etc., the spatial Configuration of the molecule can be determined. One obtains the chemically constructed force constants, bond lengths and bond angles.
From the point of view of spectral analysis, the main thing is to use the frequency of the characteristic absorption band to infer the existence of a specific group or bond in the molecule and to infer the neighboring group From the Frequency change of the characteristic absorption bandThe chemical structure of the molecule can then be determined from the bond or bonds. Of course, the quantitative analysis of the mixture and compound can also be performed by changing the intensity of the characteristic absorption band.
Given the wide range of applications of infrared spectroscopy, infrared spectrometers that record infrared spectra have also become an important research object for scientists.
The Fourier transform infrared spectrometer (FT-IR) is based on the principle of light coherence, so it is an interference spectrometer, mainly composed of a light source (silicon-carbon rod, high-pressure mercury lamp), an interferometer, a detector, a computer and other recording system ;
Most Fourier transform infrared spectrometers use Michelson interferometer, so the principle of experimental measurementThe initial spectrogram iis the interferogram of the light source.
Then the computer performs a fast Fourier transform calculation on the interferogram to get the spectrogram as a function of wavelength or wavenumber, i.e. the spectrogram. The instrument is called a Fourier Transform infrared spectrometer and is called Fourier transform infrared spectrometer.
