Absorbance of UV-irradiated BO-SA LB films

Effect of UV irradiation on the absorption spectra of Langmuir-Blodgett films obtained by a deposition of double layers of bis-ethylenedioxy-tetrathiafulvalene (BO) and stearic acid (SA) is investigated. Irreversible changes observed in the absorbance correlate with a sharp increase of the sample resistance upon irradiation. Vibrational features due to direct IR excitation and resulting from electron-molecular vibration coupling to totally symmetric internal modes of BO molecule are assigned. The spectra of UV-irradiated BO-SA LB films are interpreted within the model of two Lorentz oscillators.