Pulse radiolysis of supercritical water. 3. Spectrum and thermodynamics of the hydrated electron
Pulse radiolysis of supercritical water. 3. Spectrum and thermodynamics of the hydrated electron
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DOI：
10.1021/jp0457141
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发表时间：
2005-02-24
影响因子：
2.9
通讯作者：
Jonah, CD
中科院分区：
文献类型：
--
作者：
Bartels, DM;Takahashi, K;Jonah, CD
光谱的水合电子在加压的轻和重水的温度高达和超过临界温度的报告，波长在0.4和1.7妈妈。与先前的工作一致，在亚临界水中，光谱可以近似地由低能侧的高斯函数和高能侧的洛伦兹函数表示，但在200 ℃以上，与这种形式的偏差非常明显。随着温度的升高，光谱强烈地向红色移动。在超临界温度下，随着密度的降低，光谱略微向红色移动，高斯-洛伦兹形式是非常差的描述。应用谱矩理论可以估计电子波函数的平均大小及其动能。似乎对于低于约0.6g/cc并且低至低于0.1g/cc的水密度，电子的平均回转半径保持恒定在约3.4埃，并且其吸收最大值接近0.9eV。对于更高的密度，电子被挤压到一个更小的腔中，光谱向蓝色移动。电子水合的焓和自由能作为温度的函数导出的基础上，现有的平衡数据和绝对质子水合能来自基于簇的公共点方法。在讨论中，我们比较了有效的“大小”的水合电子来自这两种方法。
Spectra of the hydrated electron in pressurized light and heavy water at temperatures up to and beyond the critical temperature are reported, for wavelengths between 0.4 and 1.7 mum. In agreement with previous work, spectra can be approximately represented by a Gaussian function on the low-energy side, and a Lorentzian function on the high-energy side in subcritical water, but deviations from this form are very clear above 200 degreesC. The spectrum shifts strongly to the red as temperature rises. At supercritical temperatures, the spectrum shifts slightly to the red as density decreases, and the Gaussian - Lorentzian form is a very poor description. Application of spectral moment theory allows one to make an estimate of the average size of the electron wave function and of its kinetic energy. It appears that for water densities below about 0.6 g/cc, and down to below 0.1 g/cc, the average radius of gyration for the electron remains constant at around 3.4 Angstrom, and its absorption maximum is near 0.9 eV. For higher densities, the electron is squeezed into a smaller cavity and the spectrum is shifted to the blue. The enthalpy and free energy of electron hydration are derived as a function of temperature on the basis of existing equilibrium data and absolute proton hydration energies derived from the cluster-based common point method. In a discussion, we compare the effective "size" of the hydrated electron derived from both methods.