What is Raman spectrometer?
Raman spectrometer is mainly used in scientific research institutes, physics and chemistry laboratories of colleges and universities, biological and medical fields, and other optical aspects to determine and confirm the composition of research materials; it can also be used in criminal investigation and jewelry industry for drug detection and gem identification.
The instrument is known for its simple structure, simple operation, fast, efficient and accurate measurement, and is known for its low wavenumber measurement capability; it adopts a confocal optical path design to obtain higher resolution, and can perform micro-area detection on the sample surface at the um level, also can use microscopic image measurement.
When a beam of monochromatic light with a frequency of v0 shines on the sample, the molecules can scatter the incident light.
Most of the light just changes the direction of light propagation, so that it is scattered, and the frequency of the transmitted light passing through the molecule is still the same as the frequency of the incident light. At this time, this kind of scattering is called Rayleigh scattering; there is also a kind of scattered light.
It occupies about 10^-6～10^-10 of the total scattered light intensity. Not only the propagation direction of the scattered light has changed, but the frequency of the scattered light has also changed, which is different from the excitation light (incident light).
Frequency, so the scattered light is called Raman scattering.
In Raman scattering, the frequency of the scattered light decreases relative to the frequency of the incident light, which is called Stokes scattering. Therefore, in the opposite case, the scattering with increasing frequency is called anti-Stokes scattering.
Stokes scattering is usually much stronger than anti-Stokes scattering. Raman spectrometers usually measure Stokes scattering, which is also collectively called Raman scattering.
The frequency difference v between the scattered light and the incident light is called the Raman shift. The Raman shift has nothing to do with the frequency of the incident light, it is only related to the structure of the scattering molecule itself.
Raman scattering is caused by changes in molecular polarizability (changes in the electron cloud).
The Raman shift depends on the change of molecular vibrational energy level. Different chemical bonds or groups have characteristic molecular vibrations. ΔE reflects the change of the specified energy level, so the corresponding Raman shift is also characteristic.
This is the basis that Raman spectroscopy can be used as a qualitative analysis of molecular structure.
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