Table of Contents
Laser Chemistry
Volume 3, Issue 1-6, Pages 279-292

Studies of Molecular Adsorbates at Interfaces by Optical Second-Harmonic Generation

1Department of Physics, University of California, Berkeley 94720, California, USA
2Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley 94720, California, USA

Copyright © 1983 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Optical second-harmonic generation (SHG) is surface-specific and has the sensitivity to detect submonolayers of molecules. It can be applied to study molecular adsorbates at the interface between any two centrosymmetric media. This has been demonstrated by using dye and p-nitrobenzoic acid (PNBA) molecules adsorbed on smooth fused quartz substrates as examples. With resonant SHG, the S0S2 transition of the adsorbed dye molecules was measured. From the polarization dependence of the SHG, the orientation of PNBA at both the air/quartz and the ethanol/quartz interfaces was deduced. By varying the concentration of PNBA in ethanol, an adsorption isotherm for PNBA at the ethanol/quartz interfaces was also obtained.