Raman lidars
Measuring atmospheric gas with LIDAR

According to classical electromagnetic theory, Raman scattering results from the interaction of light with molecules whose polarizability varies during their natural vibrational or rotational movements. These movements can induce slight periodic deformations of the electron cloud, so that the dipole moment developed under the influence of the incident field presents coupling terms between the laser frequency and the vibration and rotation frequencies of the molecules. In this case, the scattered signal contains, in addition to the Rayleigh-Cabannes scattering term (elastic scattering, i.e. without frequency change