The Saykally Group

Experimental and Theoretical Physical Chemistry

SFG/SHG Studies of Liquid Interfaces


P. Jungwirth, D. J. Tobias, J. Phys. Chem. B 105, 10468 (2001)

Interfacial chemistry can be found in myriad environments of scientific significance including biological membranes, ocean and atmospheric chemistry, and electrochemistry. In fact, molecular behavior at the interface can be drastically different than in the bulk. Of particular import is that of the air-water interface as it is involved in many atmospheric reactions. However, it is quite difficult to probe the interface, because the interfacial signal tends to be overwhelmed by the bulk signal, and thus not readily discernible. Fortunately with the advent of ultrafast laser spectroscopy, we are now able to employ second order nonlinear optical techniques, Sum Frequency Generation (SFG) and Second Harmonic Generation (SHG), to probe ions and molecules at the air-water interface. Due to necessary symmetry constraints, these techniques are interface specific and thus give no signal from bulk.