The development history of Raman spectroscopy

Indian physicist Raman irradiated benzene liquid with a mercury lamp in 1928 and discovered a new radiation spectrum: symmetrically distributed on both sides of the incident light frequency ω0, sharp sidebands with frequencies ω0-ω and ω0 ω, this It belongs to a new kind of molecular radiation, called Raman scattering, where ω is the elementary excitation frequency of the medium. Raman won the Nobel Prize in Physics in 1930 for his discovery of this new molecular radiation and many light scattering research results. At the same time, Landsberg and Mandelstad of the former Soviet Union reported that a similar phenomenon was found in quartz crystals, namely Raman scattering caused by optical phonons, called merging scattering.　　 Rocart of France, Cabens and Wood of the United States confirmed the results of Raman's observational research. However, by 1940, the status of Raman spectroscopy plummeted. Mainly because the Raman effect is too weak (about 10-6 of the incident light intensity), it is difficult for people to observe and study weak Raman scattering signals, let alone measure and study higher-order Raman scattering effects above the second level. And it is required that the volume of the sample to be tested must be large enough, colorless, dust-free, fluorescent and so on. Therefore, by the mid-1940s, the advancement and commercialization of infrared technology made the application of Raman spectroscopy decline. After 1960, the appearance of the ruby u200bu200blaser brought the research of Raman scattering into a whole new era. Because the laser has good monochromaticity, strong directivity, and high power density, using it as an excitation light source greatly improves the excitation efficiency. Become an ideal light source for Raman spectroscopy. With the improvement of detection technology and the reduction of the requirements for the tested samples, Raman spectroscopy has been widely used in various fields such as physics, chemistry, medicine, industry, etc., and has attracted more and more attention from researchers.　　 In the mid-1970s, the emergence of laser Raman probes gave vitality to micro-area analysis. Since the 1980s, Spex Company in the United States and Rrinshow Company in the United Kingdom have successively launched the Beman probe confocal laser Raman spectrometer. Due to the use of a notch filter to filter out the excitation light and suppress the stray light, it is no longer necessary to use Double monochromator or even triple monochromator, and only a single monochromator is needed, which greatly improves the efficiency of the light source, so that the power of the incident light can be very low, and the sensitivity is greatly improved. Dilo company has launched a multi-point online industrial Raman system, which uses an optical fiber up to 200m, which makes the application range of Raman spectroscopy wider. (The above is edited by metal laser cutting machine, please refer to http://www.gnlaser.com for details)