Polarized Electron Physics

极化电子物理

• 批准号: 1206067
• 负责人: Timothy Gay
• 金额: $ 61万
• 依托单位: University of Nebraska-Lincoln
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206067&HistoricalAwards=false
• 关键词: Polarized; Electron; Physics

This project involves the study of collisions between polarized electrons (having an average spin that points preferentially in one direction) and chiral, or "handed" molecules as well as zinc atoms. The former experiments address physics questions about the dynamics of electron-molecule scattering, particularly with regard to the role played by electron spin in collisions with molecules that have a handed stereochemical structure. They will also provide important clues about the origins of biological homochirality -- the fact that all naturally-occurring DNA spirals in the same direction. The zinc experiments are being done to check the results of an experiment done recently by an Australian group in which states of zinc excited by polarized electrons exhibited linear polarization that was tilted relative to the incident beam direction in the collision. This result is forbidden by all known theories of atomic collisions; if the Australian result is reproduced, much of our basic theoretical knowledge of how electrons collide with atoms and molecules will be shown to be in error. Improved sources and analyzers of polarized electrons are being developed. We are testing increasingly compact designs of electron spin detectors. We also are studying multiphoton ionization of bulk materials such as the semiconductor GaAs to see if polarized electrons can be photoemitted from such material even when the surface has not been prepared to give it a negative electron affinity -- the normal method used to produce efficient photoemitters. This latter work holds the promise of providing new analytical tools for biological and materials research, and for industry. These experiments will have an impact beyond the immediate community of atomic, molecular, and optical science. In addition to its broader scientific implications, this work will have a significant educational component. Undergraduates working on these projects will have their first experience in scientific research. In an effort to expand the talent pool for atomic, molecular, and optical physics, women and underrepresented minorities will be especially recruited for these positions. The experiments with chiral molecules and their connection to astrobiological questions make an excellent topic for talks that will be given regularly to high school and civic groups, and that serve to illustrate the beauty of basic physics to a large lay audience.

该项目涉及极化电子（具有优先指向一个方向的平均自旋）与手性或“手”分子以及锌原子之间的碰撞研究。 前一个实验解决了关于电子-分子散射动力学的物理问题，特别是关于电子自旋在与具有手性立体化学结构的分子碰撞中所起的作用。 它们还将提供有关生物同手性起源的重要线索-所有天然存在的DNA都以相同方向螺旋的事实。 锌的实验是为了检验澳大利亚一个小组最近所做的一项实验的结果，在该实验中，被极化电子激发的锌的状态表现出相对于碰撞中的入射光束方向倾斜的线性极化。 这个结果是所有已知的原子碰撞理论所禁止的;如果澳大利亚的结果被复制，我们关于电子如何与原子和分子碰撞的许多基本理论知识将被证明是错误的。 改进的极化电子源和分析器正在研制中。 我们正在测试越来越紧凑的电子自旋探测器设计。 我们还在研究半导体GaAs等大块材料的多光子电离，看看极化电子是否可以从这种材料中光发射出来，即使表面还没有准备好给它一个负的电子亲和势-用于生产高效光电发射器的正常方法。后者的工作有望为生物和材料研究以及工业提供新的分析工具。这些实验的影响将超越原子、分子和光学科学的直接社区。除了更广泛的科学影响外，这项工作还将具有重要的教育意义。参与这些项目的本科生将获得第一次科学研究经验。为了扩大原子、分子和光学物理学的人才库，将特别招聘妇女和代表性不足的少数民族担任这些职位。手性分子的实验及其与天体生物学问题的联系是一个很好的话题，将定期给高中和民间团体，并有助于说明基础物理学的美丽，以大量的外行观众。