Inelastic Cross Sections for Low-Energy Electrons in Liquid Water: Exchange and Correlation Effects
Inelastic Cross Sections for Low-Energy Electrons in Liquid Water: Exchange and Correlation Effects
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DOI：
10.1667/rr13362.1
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发表时间：
2013-11-01
影响因子：
3.4
通讯作者：
Nikjoo, Hooshang
中科院分区：
文献类型：
--
作者：
Emfietzoglou, Dimitris;Kyriakou, Ioanna;Nikjoo, Hooshang
低能电子在放射治疗和生物学中发挥着重要作用，因为它们是吸收剂量的最大贡献者。然而，还没有一个简单的理论来描述低能电子与凝聚态介质的相互作用。本文提出了一种新的方法，包括交换和相关（XC）在低能量（低于类似10千电子伏）的背景下的非弹性电子散射的影响的电介质理论。具体而言，液态水的介电响应函数的光学数据模型的开发，超越了随机相位近似（RPA）占XC效应使用的多体局部场校正（LFC）的概念。它表明，实验的能量损失函数的液体水可以复制到RPA色散关系包括XC效应（到二阶）计算的随时间变化的局域密度近似与声子诱导的增宽在N。D. Mermin松弛时间近似额外的XC效应相关的入射和/或撞击电子包括通过顶点校正计算的修改后的哈伯德公式的交换只LFC。在第一玻恩近似下，本XC修正引起了显着更大的减少（类似于10-50%）的非弹性截面相比，常用的莫特和Ochkur近似，同时也产生更好的协议与最近的实验数据为无定形冰。目前的工作提供了一个可管理的，但严格的方法，包括非玻恩效应在计算非弹性截面的低能电子在液态水，由于其通用性，可以很容易地扩展到其他凝聚介质。(C)2013年，辐射研究学会
Low-energy electrons play a prominent role in radiation therapy and biology as they are the largest contributor to the absorbed dose. However, no tractable theory exists to describe the interaction of low-energy electrons with condensed media. This article presents a new approach to include exchange and correlation (XC) effects in inelastic electron scattering at low energies (below similar to 10 keV) in the context of the dielectric theory. Specifically, an optical-data model of the dielectric response function of liquid water is developed that goes beyond the random phase approximation (RPA) by accounting for XC effects using the concept of the many-body local-field correction (LFC). It is shown that the experimental energy-loss-function of liquid water can be reproduced by including into the RPA dispersion relations XC effects (up to second order) calculated in the time-dependent local-density approximation with the addition of phonon-induced broadening in N. D. Mermin's relaxation-time approximation. Additional XC effects related to the incident and/or struck electrons are included by means of the vertex correction calculated by a modified Hubbard formula for the exchange-only LFC. Within the first Born approximation, the present XC corrections cause a significantly larger reduction (similar to 10-50%) to the inelastic cross section compared to the commonly used Mott and Ochkur approximations, while also yielding much better agreement with the recent experimental data for amorphous ice. The current work offers a manageable, yet rigorous, approach for including non-Born effects in the calculation of inelastic cross sections for low-energy electrons in liquid water, which due to its generality, can be easily extended to other condensed media. (C) 2013 by Radiation Research Society