RUI: Negative Ion Photodetachment Spectroscopy and Lifetimes

摘要：本项目将实验研究负离子的性质，负离子是指带有一个额外电子的原子或分子。负离子在各种物理情况下都很重要，包括化学反应、行星和恒星的大气以及电等离子体。该项目的主要目标是提高对电子如何在原子尺度上相互作用（“电子相关性”）的理解——这是量子力学的一个非常重要的方面，在原子和分子的结构中起着关键作用。在丹尼森大学和瑞典DESIREE国家实验室的实验中，激光将被用来激发或分离负离子上的电子；激光提供精确控制的输入能量来探测离子内的电子相关性。研究结果将建立基础物理化学数据库，为最先进的理论原子结构计算提供有价值的测试，并对动态多体相互作用产生关键见解，这是物理、化学、材料科学和纳米技术等广泛领域感兴趣的主题。本科生将参与研究的各个方面，为年轻科学家提供尖端电子，激光和计算机方面的重要技术培训，并提高他们在科学，技术和工程方面的高级学习和未来职业的能力。摘要：光子与负离子的相互作用将在一系列光激发和光剥离实验中进行研究。负离子中的多余电子主要由电子相关效应束缚，因此负离子为这些多体相互作用的详细原子物理计算提供了肥沃的试验场。丹尼森大学的离子束可调谐红外激光系统将用于共振双光子分离光谱法测量钍负离子的多重束缚态。利用低温静电离子存储环DESIREE，将在瑞典斯德哥尔摩大学进行镧在负离子中的激发态寿命和衰变过程的补充实验。研究钍和镧是很重要的，因为它们是激光冷却的有希望的候选国，这还没有在负离子上实现，但有可能通过交感碰撞冷却为广泛的带负电荷的物种开辟超冷制度。教职员工和学生研究人员还将使用光剥离阈值光谱来测量铅和铊的电子亲和力的同位素变化，这对电子相互作用和与原子核的相互作用都很敏感。高度相关负离子中的动态多电子相互作用继续挑战着对原子结构的基本理解，本项目将把现有的实验数据扩展到更复杂的负离子体系，刺激新的理论研究，并直接解决该领域紧迫的开放性问题。这项资助将加强丹尼森大学（本科学院）的研究和教学基础设施，并为学生提供宝贵的实验研究经验和技术培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

General audience abstract:This project will experimentally investigate the properties of negative ions, which are atoms or molecules with an extra electron. Negative ions are important in a variety of physical situations including chemical reactions, the atmospheres of planets and stars, and electrical plasmas. The primary goal of the project is to improve the understanding of how electrons interact with each other on the atomic scale (“electron correlation”) — a very important aspect of quantum mechanics that plays a key role in the structure of atoms and molecules. In experiments at Denison University and at the DESIREE national lab facility in Sweden, laser light will be used to excite or detach electrons from negative ions; the laser supplies a finely controlled amount of input energy to probe electron correlations within the ions. The results will build the fundamental physical chemistry database, provide valuable tests of state-of-the-art theoretical atomic structure calculations, and yield key insights into dynamical many-body interaction, which is a topic of interest for a broad range of fields in physics, chemistry, materials science, and nanotechnology. Undergraduate students will participate in all aspects of the research, providing significant technical training for young scientists in cutting-edge electronics, lasers, and computers, and enhancing their ability for advanced study and future careers in science, technology, and engineering. Technical audience abstract:The interactions of photons with negative ions will be investigated in a series photoexcitation and photodetachment experiments. The extra electron in a negative ion is bound predominantly by electron correlation effects and therefore negative ions provide a fertile testing ground for detailed atomic physics calculations regarding these multi-body interactions. An ion beam–tunable infrared laser system at Denison University will be used to measure multiple bound states of the negative ion of thorium with resonant two-photon detachment spectroscopy. Complementary experiments of excited state lifetimes and decay processes in the negative ion of lanthanum will be performed at Stockholm University in Sweden using the cryogenic electrostatic ion storage ring DESIREE. Thorium and lanthanum are important to investigate because they are promising candidates for laser cooling, which has not yet been achieved with negative ions but could potentially open up the ultracold regime for a wide range of negatively-charged species through sympathetic collisional cooling. The faculty and student researchers will also use photodetachment threshold spectroscopy to measure isotope shifts in the electron affinities of lead and thallium, which are sensitive to interactions of electrons both with each other and with the nucleus. The dynamic multi-electron interactions in highly-correlated negative ions continue to challenge the fundamental understanding of atomic structure, and this project will extend the available experimental data to more complex negative ion systems, spur new theoretical studies, and directly address pressing open questions in the field. Support from this grant will enhance the research and teaching infrastructure of Denison University (an undergraduate college) and provide students with valuable experimental research experiences and technical training.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.