Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
Phys Rev Lett. 2012 Sep 14;109(11):115705. doi: 10.1103/PhysRevLett.109.115705.
We mapped the relaxation times of inter- and intramolecular correlations in o-terphenyl by a quasielastic scattering method using nuclear resonant scattering of synchrotron radiation. From the obtained map, we found that the slow β process is decoupled from the α process at 278 K, and this temperature is clearly below the previous decoupling temperature of 290 K, at which the α-relaxation dynamics changes. Then, it was also concluded that sufficient solidlike condition achieved by further cooling from 290 K is required to decouple the slow β process from the α process and, due to the difference of the length scales between the α and the slow β processes, these two averaged relaxation times <τ> are concluded not to cross as an extrapolation assumed so far. Furthermore, evidence of the restricted dynamics of the slow β process could be obtained as an anomalous momentum transfer (q) dependence of <τ>(<τ> ∝q(-2.9)) at 265 K, observed at q values of 18-48 nm(-1).
我们通过使用同步辐射的核共振散射，通过准弹性散射方法绘制了邻三联苯中分子间和分子内相关的弛豫时间图谱。从获得的图谱中，我们发现 278 K 时慢β过程与α过程解耦，而这个温度明显低于之前的 290 K 解耦温度，在这个温度下，α松弛动力学发生变化。然后，我们还得出结论，需要从 290 K 进一步冷却以达到足够的固态条件，才能将慢β过程与α过程解耦，并且由于α和慢β过程的长度尺度不同，这两个平均弛豫时间<τ>不会像迄今为止假设的那样交叉。此外，在 265 K 时，在 18-48nm(-1)的 q 值下观察到<τ>(<τ>∝q(-2.9))与动量传递(q)的异常依赖性，可以得到慢β过程受限动力学的证据。
