Using femtosecond time-resolved luminescence spectroscopy, we have observed a wave-packet oscillation in an adiabatic potential well associated with a self-trapped exciton ͑STE͒. We have investigated the STE luminescence band of a quasi-one-dimensional halogen-bridged platinum complex ͓Pt͑en͒ 2 ͔͓Pt͑en͒ 2 Br 2 ͔(ClO 4 ) 4 . In the time evolution of the luminescence, we have observed an oscillation with a period of about 300 fs. This result shows the formation of a wave packet and its oscillation, which is damped with the time constant of about 430 fs. The STE's have a lifetime of about 5.5 ps at room temperature.

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A method for quantitative analysis of piezomodulation spectra of a thin film on a substrate, including the internal reflection in the system, is presented. This method is applied to Langmuir–Blodgett (LB) films of copper phthalocyanine (CuPc) derivatives on glass substrates. A uniaxial stress was applied along the symmetry axis of the film. The spectra were measured in the region from 1.5 to 2.4 eV in three configurations; transmission, reflection from the film side, and reflection from the substrate side. The optimum Lorentzian parameters and their changes due to the stress are determined by the least-mean-square fit. The microstructures and electronic states of the LB film are discussed from the stress effects. The very small feature, which is hardly identified in the absorption spectra because of the large Frenkel exciton band, is attributed to a charge transfer (CT) excitation.