Interaction of Low-Energy Positrons with Atoms and Molecules

该项目的重点是使用高分辨率、基于陷阱的正电子束和专门设计的技术对低能正电子与原子和分子的相互作用进行实验研究，以研究散射和湮灭过程。 这项工作预计将对原子物理学的重要方面产生根本性的影响，包括开发处理电子-正电子相关性的方法，以及理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天体物理学感兴趣的材料和建模过程。 在这些研究中使用的正电子束具有~ 40 meV的能量分辨率，FWHM，并且在50 meV以上的能量中可调谐。 新的实验能力包括加热和冷却原子和分子目标（从100 - 800 K）的能力。目前正在开发更高能量分辨率的光束。正电子-分子碰撞中正电子湮灭的最新研究结果为正电子-分子结合的理论预测提供了新的研究课题，包括精确检验正电子-分子结合的理论预测。研究的关键主题包括定量地理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布起作用时，正电子在大分子上的湮灭。 其他计划的研究课题包括研究新的目标，包括大烷烃和多环芳烃分子，碳60和金属原子。虽然该项目侧重于反物质（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，它寻求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，预计这些结果将在其他科学领域和各种技术应用中产生进一步的影响。 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素分子和正电子素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，例如开发新的方法来识别大分子，以及更深入地了解用于研究材料的正电子工具。该项目还在其他领域产生了额外的影响。 该研究积极参与各级学生和博士后研究人员，从实验的规划到研究成果的传播。该项目涉及小规模实验，是科学和技术人员的一个极好的培训场所。 这项工作是广泛传播的，不仅对物理观众，而且对那些参与等离子体，化学，材料科学和气体电子学研究。 参与这个项目的研究人员继续促进与实验学家和理论家就共同感兴趣的问题进行积极的对话。S.以及其他一些国家。 小组成员经常就研究过程中获得的科学成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咨询。

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.