Interaction of Low-Energy Positrons with Atoms and Molecules

这个项目主要是利用高分辨率的陷阱正电子束和专门设计的技术来研究散射和湮灭过程，以实验研究低能正电子与原子和分子的相互作用。这项工作预计将对原子物理的重要方面产生根本性影响，包括开发处理电子-正电子关联的方法，以及了解正电子与原子和分子的结合。这些结果与低能正电子的许多应用有关，包括开发新的方法来表征材料和对天体物理感兴趣的建模过程。这些研究中使用的正电子束的能量分辨率为~40 meV，半高宽，在50 meV以上的能量范围内可调。新的实验能力包括加热和冷却原子和分子目标的能力(从100-800K)。一种更高能量分辨率的波束目前正在开发中。最近关于正电子-分子碰撞中正电子湮灭的研究结果为研究提供了新的课题，包括对正电子-分子结合的理论预测进行精确的检验。这项研究的关键主题包括定量地了解正电子与普通物质的结合，以及当分子内振动能量重新分配起作用时，大分子上正电子的湮灭。其他计划中的研究课题包括研究新的目标，包括大分子烷烃和多环芳香族分子、碳-60和金属原子。虽然这个项目侧重于反物质(正电子)与普通物质的低能相互作用的各个方面，但从更广泛的角度来看，它试图建立反物质与物质相互作用的定量物理和化学描述的各个方面。因此，这些成果预计将在其他科学领域和广泛的技术应用方面产生进一步的影响。基础物理学的例子包括反氢的形成，在实验室中产生正电子分子和正电子原子的玻色凝聚气体，以及涉及正电子的天体物理过程。这项工作还将有助于实现低能正电子的技术应用，如开发电离大分子的新方法，并加深对基于正电子的工具的理解，以研究材料。该项目在其他领域也有其他影响。从实验计划到研究成果的传播，各个层次的学生和博士后研究人员都积极参与研究。该项目涉及小规模实验，是科技人员的极好培训基地。这项工作被广泛传播，不仅面向物理学观众，也面向从事等离子体、化学、材料科学和气体电子学研究的人。参与该项目的研究人员继续促进与美国和其他一些国家的实验者和理论家就共同感兴趣的问题进行积极对话。该团队成员经常就研究过程中获得的科学结果和其他技术信息的实际影响向学术和工业研究人员提供建议。

This project focuses on experimental studies of the interaction of low-energy positrons with atoms and molecules using a high-resolution, trap-based positron beam and specially designed techniques to study scattering and annihilation processes. The work is expected to have fundamental impacts on important facets of atomic physics, including the development of methods to treat electron-positron correlations and understanding positron binding to atoms and molecules. The results are relevant to many applications of low energy positrons including the development of new methods to characterize materials and modeling processes of astrophysical interest. The positron beam to be used in these studies has an energy resolution ~ 40 meV, FWHM and is tunable in energy from 50 meV upwards. New experimental capabilities include the ability to heat and cool atomic and molecular targets (from 100 - 800 K). A higher energy resolution beam is currently under development. Recent results on positron annihilation in positron-molecule collisions provide new topics for study, including making precise tests of theoretical predictions for positron-molecule binding. Key themes of the research include understanding quantitatively positron binding to ordinary matter and the annihilation of positrons on large molecules when intramolecular vibrational energy redistribution is operative. Other planned research topics include studies of new targets including large alkane and polycyclic aromatic molecules, carbon-60, and metal atoms. While this project focuses on aspects of the low-energy interaction of antimatter (positrons) with ordinary matter, in the broader view, it seeks to establish aspects of a quantitative physical and chemical description of the interaction of antimatter with matter. Consequently, the results are expected to have further impacts in other areas of science and in a wide variety of technological applications. Fundamental-physics examples include the formation of antihydrogen, the creation in the laboratory of positronium molecules and Bose-condensed gases of positronium atoms, and astrophysical processes involving positrons. The work will also help to enable technological applications of low energy positrons, such as developing new methods to ionize large molecules and in providing a deeper understanding of positron-based tools to study materials.This project also has additional impacts in other areas. The research actively involves students and post-doctoral researchers at all levels, from the planning of experiments to the dissemination of research results. The project involves small-scale experiments that are an excellent training ground for scientific and technical personnel. The work is communicated broadly, not only to physics audiences but also to those involved in plasma, chemical, and materials science, and gaseous electronics research. The researchers involved in this project continue to foster active dialogue with experimentalists and with theorists working on problems of mutual interest, both in the U. S. and in a number of other countries. Members of the team frequently advise academic and industrial researchers on practical implications of the scientific results and other technical information gained during the course of this research.