ABSTRACT
When light is irradiated to molecules or small particles (d λ), there appear two types of scatterings: elastic scattering and inelastic scattering. The elastic scattering is called Rayleigh scattering and the inelastic one Raman scattering.[5.1] As shown in Figure 5.1, there is no energy exchange between the incident light and molecules in Rayleigh scattering; but energy exchanges corresponding to molecular rotational and/or vibrational (ro-vibrational) energies occur in Raman scattering. Because of those energy exchanges, wavelengths of Raman scattering light are shifted by those energies. The shift in energy gives information about molecules, and their spectra are often called “molecular —ngerprints.” The wavelength shifts are unique for each individual molecule, and thus multiple species detection is possible in many applications.
