MOLECULAR-ORIENTATION IN MIXED MONOLAYERS OF HEMICYANINE AND FATTY-ACID AT AN AIR-WATER-INTERFACE STUDIED BY 2ND HARMONIC-GENERATION

The molecular orientation of mixed monolayers consisting of hemicyanine dye and arachidic acid at an air/water interface is studied by optical second harmonic generation. It was found that the average molecular tilt angle with respect to the surface normal is almost unchanged throughout the compression process, and is smaller in a monolayer containing a higher fraction of hemicyanine. The effective local field factor was also evaluated as a function of surface number density and was found to agree qualitatively with the theoretical prediction. © 1990 The Japan Society of Applied Physics.