ABSTRACT
When an intense luminous monochromatic ray goes through a transparent medium, a fraction of light is scattered by the molecules which are present. Raman discovered that a part of light could be scattered laterally with changes in its wavelength (or frequency). One observes in the obtained spectrum: a ray of frequency ν0 (the ray of the incident light) - a series of other rays located symmetrically on both sides of the preceding ray. Their frequency are ν0±ν1, ν0 ±ν2,ν0 ±ν2, etc. These rays are Raman’s rays. The intervals between the rays are characteristic of the chemical nature of the substance. The chapter recalls also that the method is based upon visible and near-infrared radiation and that the selection rule which governs the phenomenon is such that there must be a change in the polarizability in the sample molecule accompanying the absorption. Raman’s spectroscopy completes the information provided by the spectroscopy IR. It can be useful in the fingerprint identification of samples. It is also interesting in functional analysis. It can recognize the groups C-Cl, C═C, etc.
