Lichtabsorption von Farbstoff-Molekülpaaren in Sandwichsystemen aus monomolekularen Schichten

The absorption spectra of cyanine-like dye molecules in monolayer assemblies are investigated. Pairs between two different dye molecules were obtained by superposing monolayers containing the first and second dye respectively. The spectra of these aggregates are compared with the spectra of the corresponding monomers. The spectral shifts are calculated theoretically using a perturbation approach based on the timedependent Schrödinger equation. The electronic interaction integrals are calculated from wave functions given by the onedimensional electron gas theory making allowance for the polarization of the π-electrons and the solvent. A quantitative agreement between predicted and observed shifts and intensity changes is found. It is concluded from our experiments that during the coating process of the second dye layer the dye molecules in this layer are able to diffuse within the layer to form pairs with the dye molecules fixed in the first layer.