 The four combinations give rise to four different intensities given by

where index formula_4 is of the interfacial formula_49-plane, and formula_50 and formula_51 are the linear and nonlinear Fresnel factors.By taking the tensor elements and applying the correct transformations, the orientation of the molecules on the surface can be found.Since SFG is a higher order function, one of the main concerns in the experimental setup is being able to generate a signal strong enough to detect, with discernible peaks and narrow bandwidths.