Séminaire Théorie

Mardi 12 Décembre 2017 à 11h00.

Atomistic insights into second harmonic scattering of aqueous solutions

''Second-harmonic scattering (SHS) experiments provide a unique approach to selectively probe the molecular structure of aqueous interfaces, including electrolyte solutions, the cell environment and liquid/solid interfaces. Despite tremendous progress, interpretation of SHS experiments remains challenging, because a clear picture of the underlying intermolecular correlations and of the nonlinear molecular optical response β responsible for the SHS signal is lacking. Two central assumptions often made in analyzing SHS experiments are that the scattering in bulk molecular liquids is not sensitive to intermolecular correlations (i.e. it is incoherent) and that β is not affected by fluctuations in the local electric field induced by neighbouring molecules. We have challenged both assumptions by means of atomistic simulations of aqueous solutions. Specifically, we show that i) second harmonic scattering probe angular and radial correlations also in bulk liquids and ii) fluctuations due to solvation and zero-point motion dramatically affect β. These findings may potentially change the way SHS experiments are interpreted. They also provide a framework to combine nonlinear light scattering experiments and simulations in order to shed light on the molecular structure of complex liquids and aqueous interfaces.''