Abstract

Sum frequency generation (SFG) and second harmonic generation (SHG) have now been well established as versatile surface-sensitive probes. However, since the resonant behavior of χ⁽²⁾ (2ω) can provide spectroscopic information about a surface or molecules adsorbed on a surface, only the electronic transitions of the molecules or the surface structure can be probed.^1,2 That is why this technique is not very useful to identify or selectively monitor molecular surface species. On the other hand, vibrational spectroscopy by SFG is more suitable for selective studies of adsorbed molecules and their interaction with the substrate.

© 1994 IEEE