Theory of Positron Annihilation in Solids
Theory of Positron Annihilation in Solids
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DOI：
10.1103/revmodphys.28.308
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发表时间：
1956-07
影响因子：
44.1
通讯作者：
R. A. Ferrell
中科院分区：
文献类型：
--
作者：
R. A. Ferrell
~~湮灭过程本身可以认为在量子电动力学的基础上得到了很好的理解。量子电动力学对电子偶素性质的预言在稀气体中得到了惊人的验证，在稀气体中，电子偶素原子可以被视为一个孤立的两体系统，几乎没有来自气体中其他原子的干扰。特别是多伊奇及其同事的实验，建立了电子偶素基态精细结构分裂的辐射修正，以令人印象深刻的精度证实了量子电动力学的预言。这样的实验使人们对使用湮没过程作为研究其他情况下正电子与物质相互作用的工具有了相当大的信心。多伊奇、德贝内代蒂和科本曾对正电子湮没的一般问题作过综述。近年来，正电子湮没作为一种实验工具在固态研究中的应用已得到相当大的发展，我们也致力于这一课题。“在这里，湮灭过程被用来研究湮灭之前的低能电子相互作用。使用正电子作为工具的一大优点是，高能正电子可以穿透到样品内部，然后被阻止，成为电子系统的真实的成员。这一切都发生得非常快，从那时起，人们只需要考虑与周围物质的低能非相对论相互作用。正如稍后更详细讨论的，湮灭速率和所发射的湮灭光子的总动量的分布在许多情况下仅取决于正电子波函数乘以被湮灭电子的波函数的乘积。因此，寿命和动量分布的实验测量给出了关于样品内部的有用信息。正电子湮灭的一个重要优点是湮灭过程中包含的信息以高能伽马射线的形式传递给观察者，而这些伽马射线的逃逸没有明显的衰减。
~~ the annihilation process itself can be considered to be well understood on the basis of quantum electrodynamics. The predictions of quantum electrodynamics in regardto the properties of positronium have been strikingly verified in dilute gases, where the positronium atom can be treated as an isolated two-body system with little interference from the other atoms of the gas. The experiment of Deutsch and co-workers, which established the radiative corrections in the fine structure splitting of the ground state of positronium, in particular, has con6rmed with impressive accuracy the prediction of quantum electrodynamics. Such experiments have given one considerable confidence in the use of the annihilation process as a tool for the investigation of the interaction of positrons with matter under other circumstances. Surveys of the gen-eral subject of positron annihilation have been given by Deutsch'and by DeBenedetti and Corben.'Re-cently the application of positron annihilation as an experimental tool in solid state investigations has been considerably developed, and we con6ne ourselves to this topic." Here the annihilation process is used to investigate the low-energy electronic interactions which precede the annihilation.One of the great virtues of the use of positrons as a tool is that a high-energy positron can penetrate into the interior of the sample and then be stopped and become a real member of the electronic system. This all happens very fast, and from then on one need only consider low-energy nonrelativistic interactions with the surrounding matter. As discussed in more detail later, the annihilation rate and the distribution in the total momentum of the annihilation photons emitted depend in many cases solely on the product of the positron wave function times the wave function of the electron being annihilated. Thus, experimental measurements of the lifetime and momentum distribution give useful informationabout the interior of the sample. An important advantage of the positron annihilation is that theinformation contained in the annihilation process is transported to the observer in high-energy gamma rays which escape without appreciable attenua-