Polarized X-ray absorption spectra of Langmuir-Blodgett films: Local structure studies of merocyanine dyes

Abstract

Polarized X-ray absorption spectroscopy has been applied to study the local structure and bonding states in Langmuir-Blodgett films of a merocyanine dye diluted with arachidic acid, using synchroton radiation and a fluorescence detection technique. Both in-plane and out-of-plane anisotropies, which decreased after annealing, were observed in the X-ray absorption near-edge structure spectra with respect to the electrical field vector. These results imply that (1) the chromophores are highly oriented with respect to the axis parallel to the dipping direction and plane and (2) these preferential orientations degrade when heat treated. The radial distribution around a chalcogen atom, obtained from the Fourier transform of the extended X-ray absorption fine structure, is interpreted in terms of the intramolecular structure of merocyanine.