New Technology for Exploring State-Dependent Reactivity in Radiative Association Reactions

探索辐射缔合反应中状态依赖性反应性的新技术

• 批准号: 2154055
• 负责人: Leah Dodson
• 金额: $ 44.59万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-05-15 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2154055&HistoricalAwards=false
• 关键词: New; Technology; Exploring; State; Dependent

In this project, funded by the Chemical Structure, Dynamics, and Mechanisms (CSDM-A) program of the Chemistry Division, Professor Leah Dodson and her students at the University of Maryland will study the reactivity of atomic metal ions with a class of neutral molecules—cyanopolyynes. Contrary to conventional chemical reactivity, the rates for these reactions are expected to increase as temperature decreases; however, this inverted temperature dependence is challenging to measure in the laboratory. The experimental challenges will be overcome by devising new instrumentation to prepare reactants at low temperatures and measure reactivity through direct detection by mass spectrometry. The results will provide insight into a class of reactions occurring in cold astrophysical objects and test theoretical predictions at a fundamental level. Graduate and undergraduate students will be involved in this multidisciplinary research, and the team will collaborate closely with faculty from nearby Prince George’s Community College to provide research opportunities for students in their associate degree program, many of whom are members of underrepresented groups. The broader impacts of this work will include a more complete picture of ion/molecule radiative association reactions that invites collaboration with theoretical chemists and contributes to the understanding of planetary and stellar evolution. This project will develop the cryogenic cooling techniques necessary to study ion/molecule radiative association reactions at low temperatures (down to 10 K). The radiative association of metal monocations (such as magnesium) and cyanopolyynes is predicted to have a rate that depends strongly on the rotational energy and dipole moment of the neutral reactant. To directly measure the temperature-dependent rates, the cold ions and molecules will be produced independently prior to reaction. Gaseous atomic metal ions will be generated in a glow-discharge ion source and trapped and cooled in a cryogenic multipole ion trap. The cyanopolyyne neutral reactant will be cooled in a buffer-gas collision cell before being injected into the ion trap. Kinetics data will be obtained from the time-dependent ion signals. The dependence of the measured rate constant on reactant rotational energy and dipole moment will provide independent data necessary to test discrepancies between theoretical methods that currently differ by up to four orders of magnitude. The project will provide opportunities for training graduate, undergraduate, and associate degree students in science, technology, engineering, and mathematics through the development of new technologies and a focus on professional development.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.

在这个由化学部化学结构、动力学和机制（CSDM-A）项目资助的项目中，马里兰大学的Leah Dodson教授和她的学生将研究原子金属离子与一类中性分子氰聚ynes的反应性。与传统的化学反应性相反，这些反应的速率预计会随着温度的降低而增加；然而，这种倒置的温度依赖性在实验室测量是具有挑战性的。通过设计新的仪器在低温下制备反应物，并通过质谱直接检测来测量反应性，将克服实验挑战。这些结果将提供对发生在冷天体物理物体中的一类反应的深入了解，并在基本水平上测试理论预测。研究生和本科生将参与这项多学科研究，该团队将与附近的乔治王子社区学院的教师密切合作，为他们的副学士学位课程的学生提供研究机会，其中许多人是代表性不足的群体的成员。这项工作的更广泛的影响将包括离子/分子辐射结合反应的更完整的图片，邀请与理论化学家合作，并有助于理解行星和恒星的演化。该项目将开发低温冷却技术，以研究低温（低至10 K）下离子/分子辐射结合反应。预测金属单体（如镁）和氰多炔的辐射缔合速率在很大程度上取决于中性反应物的转动能和偶极矩。为了直接测量温度依赖速率，冷离子和冷分子将在反应前独立产生。气态原子金属离子将在辉光放电离子源中产生，并在低温多极离子阱中被捕获和冷却。在注入离子阱之前，将氰聚烷中性反应物在缓冲气体碰撞池中冷却。动力学数据将从随时间变化的离子信号中获得。测量的速率常数对反应物旋转能量和偶极矩的依赖将为测试理论方法之间的差异提供必要的独立数据，这些方法目前相差高达四个数量级。该项目将通过开发新技术和注重专业发展，为科学、技术、工程和数学领域的研究生、本科生和副学士学生提供培训机会。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。