Interaction of Low-Energy Positrons with Atoms and Molecules

低能正电子与原子和分子的相互作用

• 批准号: 2306404
• 负责人: Clifford Surko
• 金额: $ 74.64万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2306404&HistoricalAwards=false
• 关键词: Interaction; Low; Energy; Positrons; Atoms

This research project focuses on science with positrons (the antiparticles of electrons). Positrons play an important role in basic science, including atomic, plasma and astrophysics, biology and medicine. Positrons also have many technological applications such as new techniques for mass spectroscopy, the characterization of materials, and positron emission tomography (PET), the latter to study metabolic processes and for drug design. While some aspects of positron interactions with matter are well understood, there are many outstanding questions. When positrons and electrons collide, they can ‘annihilate’ – i.e. their energy, originally in the form of mass, is converted into gamma rays. The research group has shown that positrons briefly – typically for less than one hundred millionth of a second - bind to most molecules before undergoing annihilation. The present project will carry out a more detailed study of the binding of positrons on various molecules. These positron binding studies are relevant to positron surface states on materials and the fate of positrons in PET and in the interstellar medium. In terms of scientific education and training, the research actively involves students and young 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. In previous research, the group showed that positrons bind to molecules. Two important intellectual challenges related to this phenomenon are to develop methods to treat electron-positron correlations and to better understand the role of vibrational dynamics in positron annihilation processes. One focus of the project is to gain a better understanding of positron binding to molecules, the magnitudes of binding energies, and what they depend upon. A second objective is to gain a better understanding of mechanisms for positron annihilation in molecules. This process proceeds by means of vibrational resonances and results in annihilation rates orders of magnitude greater than expected in simple collisions. The experiments will be conducted with a tunable, state-of-the-art, high-energy-resolution positron beam, developed by the research team, that is now coming to full capability. This device is expected to play an important role in making high-resolution measurements as a function of incident positron energy. It is expected to provide new insights into the critical role of molecular dynamics in resonant positron annihilation. The research group’s experimental work has motivated complementary theoretical work by groups around the world with the goal of gaining a more complete and fundamental understanding of resonant positron annihilation and positron-molecule binding.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该研究项目侧重于具有肯定的科学（电子设备的反粒子）。正电子在基础科学中起着重要作用，包括原子，等离子体和天体物理学，生物学和医学。正电子还具有许多技术应用，例如用于质谱的新技术，材料的表征和正电子发射断层扫描（PET），后来研究代谢过程和药物设计。虽然正电子与物质相互作用的某些方面众所周知，但仍有许多出色的问题。当阳性和电子碰撞时，它们可以“消灭” - 即最初以质量形式的能量转化为伽玛射线。研究小组表明，在进行歼灭之前，简短的阳性（通常不到一亿秒的时间不到一亿秒）与大多数分子结合。本项目将对阳性对各个分子的结合进行更详细的研究。这些正电子结合研究与PET和星际培养基中的材料和正电子脂肪上的正电子表面状态有关。在科学教育和培训方面，该研究积极涉及各级学生和年轻研究人员，从实验计划到扩散研究结果。该项目涉及小规模实验，这是科学和技术人员的良好培训场所。这项工作不仅广泛地传达给身体受众，而且还与参与血浆，化学和材料科学以及气态电子研究的人们传达。在先前的研究中，该小组表明阳性与分子结合。与这种现象相关的两个重要的智力挑战是开发治疗电子旋律相关性并更好地了解振动动力学在阳性歼灭过程中的作用的方法。该项目的一个重点是更好地理解与分子，结合能及其所依赖的结合的正电子结合。第二个目标是更好地理解分子中正电子歼灭的机制。该过程通过振动共振进行进行，并导致歼灭速率的数量级比简单碰撞中预期的要大。该实验将通过研究团队开发的可调，最先进的高能分辨率极光束进行，该实验现在正具有完全的能力。预计该设备将在进行高分辨率测量中起重要作用，这是事件正电子能量的函数。预计它将提供有关分子动力学在谐振正电子歼灭中的关键作用的新见解。研究小组的实验工作融合了全球小组的完整理论工作，目的是获得对共鸣正电子歼灭和拟构体 - 分子绑定的更完整和基本的理解。该奖项反映了NSF的法定任务，并通过使用基金会的知识绩效和广泛的影响来评估NSF的法定任务，并被视为诚实的支持。