Electron-Atom Scattering Dynamics

1914年，弗兰克和赫兹做了一个实验，对建立现代原子理论起了至关重要的作用。这个实验检验了电子与汞原子的碰撞，他们因此获得了1925年的诺贝尔奖。自第一次研究以来，电子-原子（分子）散射领域在复杂性和重要性方面都有了巨大的发展。这一领域日益重要的原因是发现了许多不同的自然现象，以及涉及电子-原子（分子）碰撞的技术过程。相关现象的巨大光谱包括发生在行星高层大气中的过程，发生在聚变等离子体中的过程，应用于制造半导体器件的技术以及发生在活组织中的辐射损伤。对这些现象的完全理解和相关技术过程的进一步发展需要对感兴趣的原子（分子）的电子散射进行定量表征，并为在实验室中继续研究这一领域提供动力。在这项拨款申请中，正在申请资助一项正在进行的电子与原子和分子碰撞实验研究项目。我们目前的主要兴趣集中在涉及激发态原子目标的碰撞现象，这一领域在很大程度上仍未开发，但在等离子体研究中具有很大的实用价值。我们的方法是用激光辐射对原子靶进行预激发，并测量涉及该预激发靶的碰撞过程。这些技术正在迅速发展成为碰撞研究中的重要工具，其中激光可以用作控制和探测碰撞反应的手段。在我们的例子中，除了为产生高浓度的激发散射目标提供了一种有效的机制外，激光辐射的使用使我们能够在“纯量子态”中制备受激原子。因此，我们可以阐明碰撞过程的物理学，并在最基本的层面上与新的理论模型建立联系。

In 1914, J. Franck and G. Hertz performed an experiment which played a vital role in establishing modern atomic theory.  That experiment, for which they won the Nobel Prize in 1925, examined the collisions of electrons with mercury atoms.  The field of electron-atom (molecule) scattering has grown enormously, both in sophistication and importance, since that first study.  The growing importance of this field arises from the discovery of numerous and diverse natural phenomena, as well as technological processes, which involve electron-atom (molecule) collisions.  The immense spectrum of relevant phenomena includes processes occurring in the upper atmospheres of the planets, processes occurring in fusion plasmas, techniques applied to the fabrication of semiconductor devices and occurrence of radiation damage in living tissue.  Complete understanding of these phenomena and the further development of the relevant technological processes requires the quantitative characterization of electron scattering from the atoms (molecules) of interest and supplies the motivation for the continued study of this field in the laboratory.   In this grant application, funding is being requested to support an ongoing program in the experimental investigation of electron collisions with atoms and molecules.  Our primary interest is currently focused on collision phenomena involving excited-state atomic targets, a field which remains largely undeveloped but is of great practical value in plasma studies.  Our method involves pre-excitation of the atomic target by laser radiation and the measurement of collision processes involving this pre-excited target.  Such techniques are developing rapidly as important tools in collision studies where lasers can be utilized as a means to control and probe collision reactions.  In our case, in addition to providing an efficient mechanism for the production of high concentrations of excited scattering targets, the use of laser radiation allows us to prepare the excited atom in a "pure quantum state".  We can thereby elucidate the physics of the collision process and make the connection with new theoretical models at the most fundamental level possible.