Determination of adsorption geometry on spherical particles from nonlinear Mie theory analysis of surface second harmonic generation

Although second harmonic generation is intrinsically sensitive for probing interfaces, interpreting experimental observations for the determination of interfacial properties of colloidal particles requires rigorous theoretical treatment. A generally applicable nonlinear Mie theory is expanded into higher multipolar terms for describing second harmonic scattering from the surface of spherical particles. From a nonlinear least-square fitting of the scattering angular distribution of second harmonic light from molecules adsorbed on the surface, we demonstrate the determination of molecular hyperpolarizability and adsorption geometry on the surface of nanometer- to micrometer-sized spherical particles.