correct transformations, the orientation of the molecules on the surface can be found. Experimental setup 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. Pico-second and femto-second pulse width lasers are used due to being pulsed lasers with high peak fields. Nd:YAG lasers are commonly used. However, the bandwidth is increased with shorter pulses, forming a tradeoff for desired properties. Another limitation is the tunable range of the IR laser. This has been augmented by optical parametric generation (OPG), optical parametric oscillation (OPO), and optical parametric amplification (OPA) systems. Signal strength can be improved by using special geometries, such as a total internal reflection setup which uses a prism to change the angles so they are close to the critical angles, allowing the SFG signal to be generated at its critical angle, enhancing the signal. Common detector setups utilize a monochromator and a photomultiplier for filtering and detecting. References Vibrational spectroscopy Surface science