Raman briefly explained…

Raman spectroscopy is a non-contact analysis method for material characterization. Monochromatic light is shone into the substance to be analyzed using a laser. In addition to the irradiated wavelength (elastic Rayleigh scattering), the light scattered by the material also contains photons of other wavelengths, known as inelastic or Raman scattering. The change in energy is caused by the excitation of movements in the molecules. If we plot the wavelength and intensity of this inelastically scattered light relative to the irradiated laser light, we obtain the so-called Raman shift, given in wave numbers (cm^-1) as a spectrum.

Raman spectroscopy is therefore, like infrared spectroscopy (IR), a vibrational spectroscopic method. In contrast to IR, however, signals do not reach the detector by reflection or transmission; instead, the inelastic scattering propagates spherically in all directions, which makes installations in clear reaction approaches considerably easier because no transmission probes are required. Instead, simple immersion or even non-contact probes (e.g. installed on sight glasses) can be used.

• Method that has been established and used for years.
• Light-based and therefore non-destructive and contactless analysis possible.
• Highest accuracy and lowest detection limits.
• Perfect technology for transparent approaches, as no installation in transmission is necessary.
• Perfect technology for aqueous approaches, as water hardly interferes as a weak Raman scatterer.
• Hardly sensitive to temperature.

As with all technologies, there are also limitations: Fluorescence is an interfering background signal that can disrupt or even completely overlay the Raman molecule signals that are actually of interest. With the new timegated Raman spectroscopy, however, this problem has been successfully circumvented for some time. Raman as a laser-based method requires a safety briefing, as offered by Servantech. If moisture or water content is important, the methods of choice tend to be NIR and FT-IR.

The numerous areas of application for Raman spectroscopy range from identity verification in incoming goods to process control in the chemical and pharmaceutical industries to the identification of hazardous substances by authorities and organizations with security tasks.

Raman-Spectrometer