Medical Physics Laboratory, University of Ioannina Medical School, Ioannina, Greece.
Int J Radiat Biol. 2012 Jan;88(1-2):22-8. doi: 10.3109/09553002.2011.588061. Epub 2011 Jul 14.
We provide a short overview of optical-data models for the description of inelastic scattering of low-energy electrons (10-10,000 eV) in liquid water. The effect on the inelastic scattering cross section due to different optical data and extension algorithms is examined with emphasis on some recent developments.
The optical-data method whereby experimental optical data and theoretical extension algorithms are used to describe the dependence of the dielectric response function on energy- and momentum-transfer and obtain the Bethe surface of the material, currently represents the most used method for computing the inelastic scattering of low-energy electrons in condensed media. Two sets of experimental optical data for liquid water obtained from reflectance and inelastic X-ray scattering spectroscopy, respectively, and the extension algorithms of Ritchie, Penn, and Ashley are examined. Recent developments are discussed along with the role of corrections to the random phase approximation (RPA) of electron gas theory.
The inelastic scattering cross section in the energy range 200-10,000 eV was found to be rather insensitive (to within 10%) to the choice of optical data or the extension algorithm. In contrast, differences between model calculations increase rapidly below 200 eV with the influence of the extension algorithm being dominant.
The choice of the extension algorithm used to extrapolate optical data to finite momentum transfer and obtain the Bethe surface is crucial in modelling the inelastic scattering of electrons with energies below 200 eV. A new set of measurements on the dielectric response function of liquid water beyond the optical limit and the development of extension algorithms that will go beyond RPA by considering the effect of (short-range) electron exchange and correlation should be of some priority.
我们提供了一个简短的概述，介绍了用于描述低能电子（10-10000 eV）在液态水中非弹性散射的光学数据模型。我们重点研究了一些最新进展，考察了不同光学数据和扩展算法对非弹性散射截面的影响。
光学数据方法，即使用实验光学数据和理论扩展算法来描述介电响应函数随能量和动量传递的依赖关系，并获得材料的贝塞尔表面，目前是计算凝聚态介质中低能电子非弹性散射最常用的方法。我们考察了分别从反射率和非弹性 X 射线散射光谱获得的液态水的两套实验光学数据以及 Ritchie、Penn 和 Ashley 的扩展算法。我们还讨论了最新的发展以及对电子气理论的随机相位近似（RPA）的修正的作用。
在 200-10000 eV 的能量范围内，非弹性散射截面对于光学数据或扩展算法的选择相对不敏感（在 10%以内）。相比之下，模型计算之间的差异在 200 eV 以下迅速增加，扩展算法的影响占主导地位。
用于将光学数据外推到有限动量传递并获得贝塞尔表面的扩展算法的选择对于模拟低于 200 eV 能量的电子的非弹性散射至关重要。一些优先事项应该是对液态水的介电响应函数进行超出光学极限的新测量以及开发扩展算法，这些算法应考虑到（短程）电子交换和相关的影响，以超越 RPA。
