Structural relaxation in amorphous molecular systems' Studies with conformation

我们一直在研究冷衬底上气相沉积制备的非晶分子体系的结构和结构弛豫。在这个为期两年的项目中，我们研究了由具有构象异构体的化合物制成的样品的弛豫，以阐明分子结构变化与分子间构型变化之间的相互关系。在第一年，我们对真空系统进行了改进。在污染较少的情况下对非晶样品进行拉曼测量。在此基础上，我们对1,2-二氯ethan （DCE）进行了测量，发现即使在固体无定形状态下，DCE的间扭式分子也随着温度的升高而增加。第二年，我们继续对DCE进行了详细的研究。从间扭摩尔分数的定量估计中，我们发现室温蒸汽沉积时样品表面的温度小到几开尔文。在温度升高的初始阶段，间扭扭的增加速率很小，但随着沉积温度的升高，在一定的温度范围内，间扭扭的增加速率会加快。综合上述实验结果，我们对非晶DCE的弛豫过程进行了详细的讨论，并在J.Phys.Chem.B.上进行了报道。我们还研究了具有类似DCE构象异构体的无定形丁腈的弛豫。在本研究中，我们发现在玻璃化转变温度T_g时，拉曼带波数的温度变化方向相反。这是第一次通过光谱测量证实玻璃化转变的观测。我们在j . non - crystal . solid上报道了这些结果。目前，我们正在进一步研究一个新的现象，即当我们在接近T_g的温度下制备样品时，弛豫行为与普通的弛豫行为不同。

We have been studying structure and structural relaxation in amorphous molecular systems prepared by vapor deposition onto cold substrates. In this two-years project, we have studied the relaxation of samples made of compounds that have conformation isomers to elucidate the interrelation between the molecular structural change and the change in intermolecular configuration.In the first year, we improved the vacuum system to carry out the. Raman measurements on the amorphous samples under the condition with less amount of the contamination. Along with this work, we tried the measurements on 1,2-dichloroethan (DCE), and found interesting phenomena that the gauche molecules of DCE increased with the temperature elevation even in the solid amorphous states.In the second year, we continued the study on DCE in detail. From the quantitative estimation of the gauche mole fraction, we found that the temperature at the sample surface on deposition of room-temperature vapor was as small as few Kelvin. The rate of the increase of gauche was small in the initial period of temperature elevation, but it was accelerated above a certain region of temperature depending on the deposition temperature. Taking all such experimental results into consideration, we made a detail discussion on the relaxation process of amorphous DCE, and reported it in J.Phys.Chem.B. We also studied the relaxation of amorphous butyronitrile that has conformation isomers similar to those of DCE. In this study, we found that the temperature change of the wavenumber of a Raman-band turned to the opposite direction at the glass-transition temperature T_g. This was the first observation by which a glass transition was confirmed by spectroscopic measurements. We reported these results in J.Non-Cryst.Solid. For the moment, we are further studying a new phenomena that the relaxation behavior is different from ordinary ones when we prepare the samples at temperatures close to T_g.