Raman-scattering intensity and space luctuation of number density of molecules in amorphous molecular systems

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This work was carried out to confirm experimentally that the Raman-scattering intensity from amorphous systems is weakened by the space fluctuation of the polarizability of the sample, and thus to indicate that Raman scattering is the interfering light scattering. In the first year, a high-vacuum chamber was designed and constructed for preparing amorphous molecular films with a good structural reproducibility, and also a high-sensitivity optical system was assmbled for the Raman measurement. Then, experiments were carried out to compare the light intensities scatted from the molecular film by the elastic-scttering due to the unhomogeneity in the sample and by the Raman process. Results of these experiments suggested that the molar-intensity of Raman scattering from crystalline molecular grain might depend on te grain size and thus on the correlation function of the polarizability of the sample.In the second year, experiments were carried out for investigating the optical properties of amorphous molecular films during their preparation by the vacuum deposition on cold substrates. Light interference in the films was monitored, and was compared with the results of theoretical simulation. It was found that the amorphous films prepared at relatively high temperatures are transparent and homogeneous, but those prepared at very low temperatures tend to grow unhomogeneity in the film during the deposition. From the results of X-ray diffraction, which was carried out separately, the size of crystalline grain appearing by the annealing of the amorphous films thus prepared are 30-40 nm. Therefore, the characteristic length of the density fluctuation in the amorphous films prepared at very low temperatures are inferred to be the order of several tens of nanometer, and such unhomogeneity in the sample might be the cause of the small intensity of Raman scattering from amorphous systems. Detailed examination of the experimental results will be continued in future.