Peak Analytical, Inc.

When incident light strikes a sample, most of the photons are scattered at the same wavelength as that of the incident radiation (elastic scattering). A small fraction of the light is scattered at different wavelengths than that of the incident light (inelastic scattering). The energy difference between the incident light and the inelastic scattered light gives rise to the Raman effect. This interaction can be viewed as a perturbation of the molecule’s electric field. Raman bands result from a change in polarizability of the molecule (induced dipole moment divided by the electric field causing the induced dipole moment). The polarizability can be thought of as the deformability of the electron cloud of the molecule by the electric field. A Raman spectrum can be obtained from a sample as small as 1 micrometer, is non-destructive and a molecular level analysis technique complementary to FTIR. Reference libraries exist for Raman spectroscopy as they do for FTIR.