Raman Theory 

Raman spectroscopy is a form of vibrational spectroscopy where the compound or mineral is identified.

A monochromatic light from a laser is directed onto a sample. Most of this light scatters and remains the same frequency (Rayleigh), however a small percentage is absorbed and re-emitted as a process of vibrating (bending and stretching) the chemical bonds (Raman).

Diagram of Rayleigh and Raman scatter on a eucryptite sample.  

This process changes the frequency (energy) of the re-emitted light and this subtle shift in frequency is measured by the Raman (Raman shift). The vibrational modes and their associated energies are unique to each compound or mineral, generating a unique spectrum which may be identified through spectral matching.

Professor Spectrum

Portable Spectral Services Youtube channel that teaches about spectral technology. 
Raman Ready Series 
A series of videos on everything Raman. Learn about the theory, scan times, and demonstrations.