Abstract

IR–visible sum frequency generation (SFG) is a surface specific second-order nonlinear optical mixing process which can provide information on structure and chemistry of molecular adsorbates at either in situ or UHV interfaces.^1,2 The nonlinear susceptibility of the surface region is resonantly enhanced when the IR field is tuned across a vibrational transition in the molecular species, provided the transition is both Raman and IR active.³ We have used SFG to study the C-H stretching region (2800-3000 cm⁻¹) of a variety of adsorbates on either metal or transparent dielectric substrates.

© 1989 Optical Society of America