The Raman effect is based on scattering of light, which includes both elastic (Rayleigh) scattering at the same wavelength as the incident light, and inelastic (Raman) scattering at different wavelengths, due to molecular vibrations. Raman scattering is about a million times less intense than Rayleigh scattering. Therefore, to obtain Raman spectra, it is necessary to prevent Rayleigh scattering from overpowering the weaker Raman scattering.

Raman spectra are measured by exciting a sample using a high-intensity laser beam, with the resulting scattered light being passed through a spectrometer. The Raman shift is the energy difference between the incident light and the scattered light. In the resulting spectrum, the vertical axis is the intensity of the scattered light and the horizontal axis is the wavenumber of the Raman shift (cm-1).

The Raman shift is associated with two different energy bands. The shift at wavelengths higher than that of the incident light is termed Stokes scattering. The shift at wavelengths lower than that of the incident light is termed anti-Stokes scattering. Stokes scattering is observed in the lower wavenumber (longer wavelength) region and anti-Stokes scattering in the higher wavenumber (shorter wavelength) region. Typically, higher-intensity Stokes scattering peaks are used for analysis.