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

通过实验证实了非晶态体系的拉曼散射强度会因样品极化率的空间涨落而减弱，从而表明拉曼散射是干涉光散射。在第一年中，我们设计并建造了一个高真空室，用来制备具有良好结构再现性的非晶分子薄膜，并为拉曼测量配备了一个高灵敏度的光学系统。然后，进行实验以比较由于样品中的不均匀性而通过弹性散射和通过拉曼过程从分子膜散射的光强度。这些实验结果表明，结晶分子颗粒的拉曼散射的摩尔强度可能依赖于颗粒的大小，从而依赖于样品极化率的相关函数。第二年，我们进行了非晶分子薄膜在冷基片上真空沉积过程中的光学性质研究。监测薄膜中的光干涉，并与理论模拟的结果进行了比较。结果发现，在相对较高的温度下制备的非晶薄膜是透明的和均匀的，但那些在很低的温度下制备的薄膜往往在沉积过程中生长的不均匀性。从单独进行的X射线衍射的结果来看，通过对这样制备的非晶膜进行退火而出现的晶粒尺寸为30-40 nm。因此，在非常低的温度下制备的非晶薄膜中的密度波动的特征长度被推断为几十纳米的数量级，并且样品中的这种不均匀性可能是来自非晶系统的小的拉曼散射强度的原因。今后将继续对实验结果进行详细检查。

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.