高散射媒质中的光程可分割动态光散射研究

为研究散射光强度随光子在散射媒质中散射光程的变化，基于单散射理论与扩散波光谱理论，采用了低相干动态光散射装置对不同粒径大小的聚苯乙烯悬浮液进行研究。将测量得到的背散射光光场强度谱的线宽与相应的理论计算结果相比较发现，在短光程区域，考虑容器壁附近拖曳效应的影响后，对于不同粒径的颗粒，光程为约5倍粒子平均自由程的区域可看成为单散射区域；对于光程大于225 m的区域可看成为扩散光波区域。实验结果表明低相干动态光散射法可实现高散射媒质从单散射区域到低次散射再到扩散区域的全光程的可分割的光场强度谱测量。

Path-length-resolved dynamic light scattering in highly scattering media

Based on single scattering theory and diffusing wave spectroscopy theory, low-coher-ence dynamic light scattering was used to investigate the path-length resolved light field intensity spectra of backscattering lights from different radius particles of colloidal suspensions. The linewidths of the measured light field intensity spectra were compared with the predict results calculated from the corresponding theories. The results show that in short path-length region, the measured linewidths well agree with that of the single scattering after considering the influences of wall-drag effect close to the interface. For different radius particles, the region with the path length about 5 times of the mean-free path length can be regarded as a single scattering region, while the region with the propagated path length larger than 225 μm can be regarded as a diffusing region. It is demonstrated that the low-coherence dynamic light scattering can realize resolved path-length light field intensity spectra measurement from single scattering to diffusive scattering regions for dense suspensions.