A novel type of surface vibrational sum-frequency generation spectroscopy is presented that enables a highly specific measurement of the coupling of molecules on surfaces. With this doubly vibrationally resonant technique, two-dimensional vibrational spectroscopy of molecules on surfaces becomes possible. The technique is demonstrated for the C-O stretch vibration of CO on a ruthenium (001) surface. It allows for the determination of the intermolecular coupling strength of dipole-coupled CO molecules on the surface.

Phys. Rev. Lett.
Ultrafast Spectroscopy

Bonn, M, Hess, C, Miners, J.H, Heinz, T.F, Bakker, H.J, & Cho, M. (2001). Novel surface spectroscopy: Infrared-infrared-visible sum-frequency generation. Phys.Rev.Lett., 86, 1566–1569.