Raman Spectroscopy uses the Raman effect which is named after the Indian physicist C.V. Raman who discovered this effect in the year 1928 together with his colleague K.S. Krishnan. It is based on the phenomenon that light which is inelastic scattered by a molecule changes its energy since energy is transferred between photons and the vibration of the molecule. Thus, the scattered photon has a different energy, i.e. frequency than the incoming photon which can be measured. Where in the years after this discovery the use of the Raman effect for measurement purposes seemed to be very much limited due to the high effort to detect this very weak energy transfer today Raman spectroscopy has moved to one of the most applied spectroscopic techniques. This is due to the progress in the instrument design and the availability of useful laser light sources.
To be suitable for Raman spectroscopy the lasers have to show
- high power and frequency stability
- narrow emission bandwidth
- absence of side lines
- high beam quality