Raman spectroscopy is a technique that measures the energy of photons generated by the inelastic scattering of monochromatic excitation photons. During excitation, photons interact with the electron cloud of an analyte and a small percentage of these photons undergoes a change in energy as a result of the interaction. This energy change corresponds with molecular vibrations, rotations, and other low-frequency modes and is plotted by instrumental operating software to produce a spectrum. Raman spectroscopy is often described as a complimentary technique to FTIR because both techniques are used to probe vibrational energy levels although different selection rules allow FTIR and Raman to interrogate different sets of molecular vibrations. Raman scattering is an inherently low probability phenomenon and as such, the Raman scattering cross-section of a particular analyte will generally be several orders of magnitude less than the corresponding FTIR absorption cross-section. Practically, this means that the sensitivity of Raman spectroscopy is lower than FTIR spectroscopy. There are several advanced Raman spectroscopy techniques that generate a stronger Raman intensity when compared to spontaneous Raman scattering such as Coherent Anti-Stokes Raman Spectroscopy (CARS), Resonance Raman Spectroscopy, Surface Enhanced Raman Spectroscopy (SERS) and Tip Enhanced Raman Spectroscopy (TERS).

Raman instruments are available in a variety of configurations.  The most common instruments are bench top models but a wide variety of portable and handheld models are also available commercially. Instrument cost ranges from approximately $10,000 to approximately $100,000.