Simultaneous Determination of the Time and Space Correlations of Density Fluctuation in Glass Transition of Supercooled Liquid

本研究的目的是探讨与过冷液体玻璃化转变相关的时空密封规律的可能性。脉冲受激热散射是一种时域测量方法。ISTS通过改变散射波矢量q（改变观测长度尺度Λ = 2π/q），不仅可以直接确定密度波动的时间相关性，同时还可以确定密度波动的空间相关性。在三种典型的玻璃形成液体中观察到密度涨落；d -山梨醇，甘油和沙醇。成功地测量了密度波动的q依赖关系，并在这些材料中普遍发现了这种新现象。密度波动的弛豫时间τ_R在特定温度T_<max>（远高于玻璃化转变温度T_g）处出现异常峰。此外，我们首次发现T_<max>趋近于T_g且q随q的减小而减小，这一现象暗示了表征密度波动空间相关性的长度尺度ξ的存在。因为我们很自然地认为ξ随温度的降低而增大，所以我们认为T_<max>是ξ = Λ时的温度。

The purpose of this study is to investigate the possibility of the time-space sealing law associated with glass transition of supercooled liquid. The impulsive stimulated thermal scattering (ISTS : one of time-domain measurements) has been performed for this purpose. ISTS can determine not only the time correlation of the density fluctuation directly but also the space correlation of the density fluctuation at the same time by changing the scattering wave vector q (changing the observation length scale Λ = 2π/q).The density fluctuation has been observed in three typical glass forming liquids ; D-sorbitol, glycerol, and salol. The q dependence of the density fluctuation has been successfully measured and the new phenomenon has been found commonly in these materials. The relaxation time τ_R of the density fluctuation shows an anomalous peak at the particular temperature T_<max> (much higher than the glass transition temperature T_g). Moreover, we firstly found that T_<max> approaches T_g with decreasing in q. This phenomenon implies the existence of the length scale ξ characterizing the space correlation of the density fluctuation. Since it is natural to think that ξ is growing with decreasing in temperature, we think that T_<max> is the temperature where ξ = Λ.