Specifically, the Raman effect is a light scattering technique based on the principle that molecules scatter incident light from a highly intense light source, typically a laser source. The scattered, incidental light is usually the same wavelength as the laser light and does not provide essential data about the sample. That’s because when light hits something, most of the photons that are scattered are the same energy as the light it was hit with. This scattered light is also referred to as Rayleigh Scatter.

However, a minimal amount of light is scattered at a different wavelength than the Rayleigh Scatter and is indicative of an analyte’s chemical structure. This shorter wavelength scattered light is called Raman Scatter, or Raman effect. It is named after Sir C.V. Raman.

In other words, Raman spectroscopy is a type of molecular spectroscopy that relies on inelastic scattering (Raman Scatter) of light to detect vibrational, rotational, and other low-frequency modes in a sample.

It is used in chemistry to identify molecules by providing a structural fingerprint, represented by a Raman spectrum. This spectrum is characterized by several peaks that describe the intensity and wavelength position of the scattered light from a sample and are unique to specific molecules and materials. Each peak relates to a particular molecular bond vibration, including both individual bonds and groups of bonds.

Raman spectral libraries are often used to identify a sample based on its Raman spectrum. The libraries contain thousands of samples’ Raman spectra, collected from various positions of each sample.

Because Raman looks at the scattering of light rather than its absorption, the sample preparation is much less complex, and there are no aqueous absorption bands to throw off the data. When a monochromatic laser interacts with a sample, the light will scatter. Furthermore, these devices offer both low/medium resolution and high-resolution capabilities.