Polarization resolved second harmonic scattering of neat water in the right angle and forward scattering geometries

Abstract

Liquid water still remains an ubiquitous liquid whose molecular organization requires careful investigation. In this work, we present a study of the second harmonic scattering (SHS) intensity for two different scattering angles, namely, the forward and the right angle geometries. This method performed at optical wavelengths is indeed selective toward long correlation lengths. A polarization analysis demonstrates that it is then possible to clearly evidence a coherent component to the total SHS intensity using a fast Fourier transform analysis of the SHS intensity as a function of the fundamental angle of polarization despite its weak relative contribution. A model is then derived based on the rotational invariants to fully unravel the different contributions to the SHS intensity for the two right angle and forward angles of scattering as well as the dependence with the fundamental beam polarization angle. This model fully supports the experimental results, further confirming an azimuthal geometry of the water–water orientational correlation function in neat water.