Probing nanoscopic droplet interfaces in aqueous solution with vibrational sum-frequency scattering: A study of the effects of path length, droplet density and pulse energy

►Nonlinear light scattering spectroscopy was done on oil droplets dispersed in water. ► We examine the signal dependence on IR frequency, path length, and pulse energy. ► Maximum signal occurs for path lengths equal to the IR penetration depth. ► The spectrum is invariant to the IR energies used. ► The signal scales linearly with particle density.