RUI: Negative Ion Photodetachment Spectroscopy and Lifetimes

一般观众摘要：这个项目将对负离子的性质进行实验研究，负离子是具有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(“电子关联”)的理解--这是量子力学的一个非常重要的方面，在原子和分子结构中发挥着关键作用。在丹尼森大学和瑞典Desiree国家实验室的实验中，激光将被用来激发电子或将电子从负离子中分离出来；激光提供了精确控制的输入能量，以探测离子中的电子关联。这些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，并对动力学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方方面面，为青年科学家提供重要的尖端电子、激光和计算机技术培训，增强他们在科学、技术和工程领域的深造和未来职业生涯的能力。技术观众摘要：我们将在一系列的光激发和光分离实验中研究光子与负离子的相互作用。负离子中的额外电子主要受电子关联效应的约束，因此负离子为关于这些多体相互作用的详细原子物理计算提供了肥沃的测试基础。丹尼森大学的离子束可调谐红外激光系统将用共振双光子分离光谱测量钍负离子的多束缚态。瑞典斯德哥尔摩大学将使用低温静电离子存储环Desiree进行La负离子激发态寿命和衰变过程的补充实验。钍和镧是重要的研究对象，因为它们是激光冷却的有希望的候选者，负离子还没有实现这一点，但可能通过交感碰撞冷却为广泛的负电荷物种打开超冷区域。教职员工和学生研究人员还将使用光分离阈值光谱来测量铅和铊的电子亲和力中的同位素位移，这些亲和力对电子之间的相互作用以及与原子核的相互作用都很敏感。高关联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，该项目将把现有的实验数据扩展到更复杂的负离子系统，刺激新的理论研究，并直接解决该领域迫切的公开问题。这笔资金的支持将加强丹尼森大学(一所本科院校)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NSF的法定使命，并通过使用基金会的智力优势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.