Raman Spectroscopy

Raman spectroscopy is an optical technique that detects intrinsic vibrational, rotational and other low-frequency modes in molecules upon inelastic scattering of monochromatic light. Because different chemical functional groups scatter light at different frequencies, Raman spectroscopy can be used as a tool for chemical structure analysis, chemical fingerprinting and chemical imaging.

http://www.nature.com/subjects/raman-spectroscopy