Separating surface structure and surface charge with second-harmonic and sum-frequency scattering

We analyze the effect of an electrostatic surface charge on the angular nonlinear light scattering pattern from spherical particles in solution. An electrostatic field near a charged interface leads to a bulk-allowed third-order process, the strength of which is proportional to the electrostatic surface potential. The commonly isotropic nature of the bulk leads to a fixed angular scattering pattern with fixed intensity ratios between polarizations. We show that second-and third-order scattering effects are separable due to their different angular radiation patterns. Furthermore, nonlinear light scattering from a third-order contribution is strongest in the ppp polarization combination.