Hyper Rayleigh Scattering of Liquids : An Insight into Nanoscale Organization of Liquids

Second Harmonic Generation, the phenomenon whereby two photons at a fundamental frequency are converted into one photon at the harmonic frequency is forbidden in materials possessing inversion symmetry. It is therefore largely employed to convert frequencies in non centrosymmetric crystals or investigate interfaces. Nevertheless, liquids, although possessing inversion symmetry from the macroscopic point of view, undergo instantaneous molecular orientation fluctuations breaking this symmetry. Hence, interest has recently sparked in the investigation of the nanoscale molecular correlations using Second Harmonic Scattering (SHS), in water and electrolytes in particular.