We have studied in situ the adsorption of a soluble anionic dye polymer onto spread monolayers by means of reflection spectroscopy. We found that the adsorption is governed by the charge neutrality; the ratio of the adsorbed polymer unit and the cationic monolayer molecule is nearly 1:l for the surface density in the range of 50-77 &/monolayer molecule. On the other hand, no adsorption occurs onto an anionic monolayer. We have also investigated the adsorption kinetics of the polymer. The rate of adsorption can be reproduced very well with a simple diffusion simulation.

The validity of the local-field approximation (LFA) has been tested in hemicyanine dye Langmuir–Blodgett monolayers. Resonant structures of absorption and the second-harmonic generation revealed that LFA is adequate to describe the second-harmonic generation in the monolayers even when the intermolecular interaction is very strong (H aggregate). A simple calculation procedure is also presented which enables one to treat monolayers as a macroscopic object in a consistent manner with the microscopic structure.

The local-field approximation has been tested for a system with strong molecular correlation, i.e. H-aggregate of a dye in Langmuir-Blodgett monolayers. Both microscopic and macroscopic aspects of the approximation have been examined and found that the approximation gives adequate description of the optical properties of the system both in the linear and second-harmonic generation processes.