Experimentalphysik II, Universität Bayreuth, D-95444 Bayreuth, Germany.
J Chem Phys. 2013 Aug 28;139(8):084504. doi: 10.1063/1.4817406.
We determine the reorientational correlation time τ of a series of molecular liquids by performing depolarized light scattering experiments (double monochromator, Fabry-Perot interferometry, and photon correlation spectroscopy). Correlation times in the range 10(-12) s-100 s are compiled, i.e., the full temperature interval between the boiling point and the glass transition temperature T(g) is covered. We focus on low-T(g) liquids for which the high-temperature limit τ ≅ 10(-12) s is easily accessed by standard spectroscopic equipment (up to 440 K). Regarding the temperature dependence three interpolation formulae of τ(T) with three parameters each are tested: (i) Vogel-Fulcher-Tammann equation, (ii) the approach recently discussed by Mauro et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)], and (iii) our approach decomposing the activation energy E(T) in a constant high temperature value E∞ and a "cooperative part" E(coop)(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)]. On the basis of the present data, approaches (i) and (ii) are insufficient as they do not provide the correct crossover to the high-temperature Arrhenius law clearly identified in the experimental data while approach (iii) reproduces the salient features of τ(T). It allows to discuss the temperature dependence of the liquid's dynamics in terms of a E(coop)(T)/E∞ vs. T/E∞ plot and suggests that E∞ controls the energy scale of the glass transition phenomenon.
我们通过进行去极化光散射实验（双单色仪、法布里-珀罗干涉仪和光子相关光谱学）来确定一系列分子液体的重取向相关时间τ。我们编译了 10（-12）s-100s 范围内的相关时间，即覆盖了沸点和玻璃化转变温度 T（g）之间的整个温度间隔。我们专注于低 T（g）液体，对于这些液体，通过标准光谱设备很容易达到高温极限τ≈10（-12）s（高达 440K）。关于温度依赖性，我们测试了三个具有三个参数的τ（T）插值公式：（i）Vogel-Fulcher-Tammann 方程，（ii）Mauro 等人最近讨论的方法[Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)]，以及（iii）我们将激活能 E（T）分解为常数高温值 E∞和依赖于温度的“协同部分”E（coop）（T）的方法[Schmidtke 等人，Phys. Rev. E 86, 041507 (2012)]。基于目前的数据，方法（i）和（ii）是不够的，因为它们没有提供明显的向实验数据中明确识别的高温 Arrhenius 定律的正确转变，而方法（iii）再现了τ（T）的显著特征。它允许根据 E（coop）（T）/E∞与 T/E∞的图讨论液体动力学的温度依赖性，并表明 E∞控制着玻璃化转变现象的能量尺度。
