Jay-Gerin Jean-Paul, Lin Mingzhang, Katsumura Yosuke, He Hui, Muroya Yusa, Meesungnoen Jintana
Departement de Medecine Nucleaire et de Radiobiologie, Faculte de Medecine et des Sciences de la Sante, Universite de Sherbrooke, Sherbrooke (Quebec) J1H 5N4, Canada.
J Chem Phys. 2008 Sep 21;129(11):114511. doi: 10.1063/1.2978955.
The optical absorption spectra of the hydrated electron (e(aq) (-)) in supercritical (heavy) water (SCW) are measured by electron pulse radiolysis techniques as a function of water density at three temperatures of 380, 390, and 400 degrees C, and over the density range of approximately 0.2-0.65 g/cm(3). In agreement with previous work, the position of the e(aq) (-) absorption maximum (E(A(max) )) is found to shift slightly to lower energies (spectral "redshift") with decreasing density. A comparison of the present E(A(max) )-density data with other measurements already reported in the literature in subcritical (350 degrees C) and supercritical (375 degrees C) water reveals that at a fixed pressure, E(A(max) ) decreases monotonically with increasing temperature in passing through the phase transition at t(c). By contrast, at constant density, E(A(max) ) exhibits a minimum as the water passes above the critical point into SCW. These behaviors are explained in terms of simple microscopic arguments based on the crucial role played by local density and configurational fluctuations (associated with criticality) in providing pre-existing polymeric clusters, which act as trapping sites for electrons.
利用电子脉冲辐解技术，在380、390和400℃三个温度下，在约0.2 - 0.65 g/cm³的密度范围内，测量了超临界（重）水中水合电子（e(aq) (-)）的光吸收光谱随水密度的变化。与之前的工作一致，发现随着密度降低，e(aq) (-)吸收峰最大值（E(A(max) )）的位置略微向较低能量移动（光谱“红移”）。将当前的E(A(max) ) - 密度数据与文献中已报道的亚临界（350℃）和超临界（375℃）水中的其他测量结果进行比较，结果表明，在固定压力下，随着温度升高并经过临界温度t(c)处的相变，E(A(max) )单调下降。相比之下，在恒定密度下，随着水超过临界点进入超临界水，E(A(max) )出现最小值。这些行为可以通过基于局部密度和构型涨落（与临界性相关）在提供预先存在的聚合物簇中所起的关键作用的简单微观论点来解释，这些聚合物簇充当电子的俘获位点。
