Negative Ion Photoelectron Spectroscopy of Atomic, Molecular and Cluster Anions

原子、分子和团簇阴离子的负离子光电子能谱

基本信息

批准号：
2054308
负责人：
Kit Bowen
金额：
$ 60万
依托单位：
Johns Hopkins University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-06-01 至 2025-05-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054308&HistoricalAwards=false
关键词：
Negative Ion Photoelectron Spectroscopy Atomic

项目摘要

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) Program in the Division of Chemistry, Professor Kit Bowen and his group at Johns Hopkins University are studying the negative ions that form when an extra electron is attached to an atom, molecule, or cluster. The addition of electrons to chemical systems can make the unexpected occur, enticing seemingly impossible processes to take place. For example, electrons drive, direct, induce, and initiate an astonishing variety of transformations, including DNA damage, proton transfer, molecular activation, and a vast array of electrochemical reactions. The negative ions that result from electron attachment are also crucial actors in chemical reaction mechanisms, playing key roles in organic chemistry, electrochemistry, and radiation biology. Electron-influenced processes in complex environments are ubiquitous. For these reasons, a microscopic understanding of basic phenomena involving excess electrons is essential. To probe these phenomena, Dr. Bowen and his group use a technique called negative ion photoelectron spectroscopy to measure how tightly electrons are bound to negatively charged atoms, molecules, and clusters. The experiments reveal detailed information about both the ions and their neutral counterparts, while also providing important benchmarks for computational chemistry. Considering the wide-ranging importance of electron-driven processes, the work in Dr. Bowen’s lab has interdisciplinary appeal, with impact ranging across fields as diverse as atmospheric chemistry, catalysis, radiation chemistry and biology, astrochemistry, and mass spectrometry. Dr. Bowen’s work also makes strong contributions to education and human resource development by mentoring graduate students who will become the scientists of tomorrow, by providing undergraduates from Johns Hopkins and other colleges and universities an opportunity to participate in cutting-edge research, and by giving high school, middle school, and elementary school students a glimpse into scientific research. The outreach efforts encourage participation from groups that are underrepresented in science.Dr. Bowen’s research examines electron-induced proton transfer (EIPT) reactions, weakly-bound (diffuse) excess electron states of atoms and molecules, and the properties of transient molecular anions. For example, the research team is exploring the role of EIPT in cluster anions, where they expect the internal interactions to be governed by the excess electron. EIPT is a wide-spread, perhaps even ubiquitous electron-assisted process. The team is also examining the relationship between EIPT in ground-state molecular anions and the process of excited-state intra-molecular proton transfer (ESIPT) in neutral molecules. Dr. Bowen’s research on weakly-bound (diffuse) excess electron states examines some of the most subtle interactions in chemistry; those between electrons and atoms or molecules. In this area, the research team is studying the formation and characterization of polarizability-bound electrons in xenon atomic cluster anions and in ground state anions of buckminsterfullerene; quadrupole-bound electrons in electronically metastable atomic metal anions; and multiple Rydberg electrons in metal-ammonia cluster anions. Although the electrons are weakly bound in each of these cases, they represent steps on a staircase of progressively stronger interactions. Finally, the research team is studying transient molecular anions using a unique approach, developed by Dr. Bowen, that combines Rydberg electron transfer with anion photoelectron spectroscopy (RET-aPES). The research team uses the RET-aPES technique to form and characterize valence anions of nucleobase molecules, the Criegee intermediate, and the hydrogen iodide molecule. They are also using RET-aPES to explore the barely studied, yet fundamentally important process of Penning electron detachment. These studies foster a deeper understanding of the earliest stages of electron damage to DNA, the electrophilic properties of important atmospheric intermediates, the unexpected stability of HI anion, and collisional anion destruction processes in energetic gaseous environments, such as flames and solar atmospheres. The outcomes from this broad research project are expected to have widespread impact across many fields of science. Additionally, the project provides advanced training opportunities for graduate and undergraduate research students, while also engaging K-12 students through Dr. Bowen's outreach activities.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.

在化学系化学结构、动力学和机理 A (CSDM-A) 项目的支持下，约翰·霍普金斯大学的 Kit Bowen 教授和他的团队正在研究当一个额外的电子附着在原子上时形成的负离子、分子或簇中的电子可以使意想不到的事情发生，从而引发看似不可能的过程发生，例如，电子驱动、引导、诱导和引发各种惊人的转变，包括DNA损伤，质子转移、分子活化和电子附着产生的大量负离子也是化学反应机制的关键因素，在复杂的有机化学、电化学和辐射生物学过程中发挥着关键作用。由于这些原因，对涉及过量电子的基本现象的微观理解至关重要，鲍文博士和他的团队使用一种称为负离子光电子能谱的技术来测量电子的结合程度。这些实验揭示了有关离子及其中性伙伴的详细信息，同时也为计算化学提供了重要的基准，考虑到电子驱动过程的广泛重要性，博士的工作。鲍文的实验室具有跨学科吸引力，影响范围涵盖大气化学、催化、辐射化学和生物学、天体化学和质谱等多个领域。鲍文博士的工作还通过指导研究生为教育和人力资源开发做出了巨大贡献。通过为约翰·霍普金斯大学和其他学院和大学的本科生提供参与前沿研究的机会，并让高中生、初中生和小学生了解科学研究，鼓励他们参与，他们将成为明天的科学家。 Bowen 博士的研究研究了电子诱导质子转移 (EIPT) 反应、原子和分子的弱结合（扩散）过量电子状态以及瞬态分子阴离子的性质。研究研究小组正在探索 EIPT 在团簇阴离子中的作用，他们预计 EIPT 是一种广泛存在的、甚至可能普遍存在的电子辅助过程。基态分子阴离子和中性分子中激发态分子内质子转移 (ESIPT) 的过程 Bowen 博士对弱结合（扩散）过剩电子态的研究检查了一些最重要的问题。化学中的微妙相互作用；电子与原子或分子之间的相互作用在该领域，研究小组正在研究氙原子簇阴离子和巴克明斯特富勒烯基态阴离子中的极化束缚电子的形成和表征。亚稳态原子金属阴离子；以及金属氨簇阴离子中的多个里德伯电子，尽管电子在每种情况下都是弱结合的，但它们代表了楼梯上的台阶。最后，研究小组正在使用 Bowen 博士开发的独特方法研究瞬态分子阴离子，该方法将里德伯电子转移与阴离子光电子能谱 (RET-aPES) 相结合。他们还使用 RET-aPES 来探索几乎没有研究过但极其重要的过程。这些研究促进了对 DNA 电子损伤的最早阶段、重要大气中间体的亲电子特性、HI 阴离子的意外稳定性以及高能气体环境（例如火焰和太阳）中的碰撞阴离子破坏过程的更深入的了解。此外，该项目还为研究生和本科生提供高级培训机会，同时还通过 Bowen 博士的外展活动吸引了 K-12 学生。本次获奖通过使用基金会的智力价值和更广泛的影响审查标准进行评估，NSF 的法定使命被认为值得支持。