Cold Controlled Reactions between Molecular Ions and Radicals

在这项由化学系化学结构、动力学和机理(CSDM-A)计划资助的奖项中，科罗拉多大学的希瑟·莱万多夫斯基教授和她的研究生和本科生同事正在研究稳定和活性自由基分子与离子的碰撞。这个项目的独特之处在于，离子(有时是分子)已经被减慢到令人难以置信的低速度。这些实验室条件模拟了星际介质(ISM)中的环境。用这些低能量制备孤立离子和/或分子的困难排除了在ISM中研究化学的任何重要的实验工作；这一研究领域实际上是一个未知的前沿。这样的研究可能会引导人们了解ISM中可能发生的化学反应类型，并作为对低能碰撞过程计算模型的异常灵敏的检查。在莱万多夫斯基小组工作的学生接受了大量实验室方法的培训，包括真空科学、电子学和仪器设计和建造。莱万多夫斯基教授和她的团队还参与了一个与高级实验室物理协会(Alpha)合作的项目，该项目将在科罗拉多大学开设Alpha沉浸式课程，以帮助高等教育教师在教师机构现有的实验中开发基于建模的方法。希瑟·莱万多夫斯基和她的研究小组进行了低能离子-自由基分子碰撞动力学实验，以探索这些物种的反应性。这些实验模拟了星际介质低温环境中的条件。初步实验研究了氢和一氧化氮与在离子陷阱中冷却的钙(+)离子(处于各种电子状态)的反应。在最雄心勃勃的实验中，研究了非常慢的自由基分子与冷却和捕获的分子离子之间的反应。自由基(OH、CH、NH)通过激光光解或脉冲放电在分子束中产生。利用莱万多夫斯基实验室开发的新型连续波减速器，用一系列减速器电极减缓这些自由基的速度。减慢的分子进入离子陷阱(例如线性Paul陷阱)，在那里它们与一群冷却的离子相互作用。进行诊断(离子的光学成像、产品的破坏性飞行时间质谱仪等)。要研究的离子包括：单电离物种：乙炔、氨、甲烷、羟基(OH+)和亚甲基(CH+)。莱万多夫斯基研究小组包括本科生积极参与真实的研究。除了她的实验工作，莱万多夫斯基教授还与科罗拉多大学物理教育小组的阿尔法和博士后研究员合作，开发和运营一个研讨会，帮助大量高等教育教职员工将建模纳入教育工作者自己的实验室课程。

In this award, funded by the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry, Professor Heather Lewandowski of the University of Colorado and her graduate and undergraduate student colleagues are studying the collisions of stable and reactive radical molecules with ions. The unique aspect of this project is that the ions (and sometimes the molecules) have been slowed down to incredibly low velocities. These laboratory conditions mimic the environment in the interstellar medium (ISM). The difficulty of preparing isolated ions and/or molecules with these low energies has precluded any significant experimental work being done to study the chemistry in the ISM; this area of investigation is a virtually uncharted frontier. Studies like this could lead the way to understand what kinds of chemical reactions can take place in the ISM, and serve as extraordinarily sensitive checks of computational models of low energy collisional processes. Students working in the Lewandowski group receive training in a large number of laboratory methods, including vacuum science, electronics, and instrument design and construction. Prof. Lewandowski and her group are also involved in a program with the Advanced Lab Physics Association (ALPhA) to run an ALPhA Immersion course at University of Colorado to assist higher-education instructors in developing a modeling-based approach into existing experiments from the instructors' institution.Prof. Heather Lewandowski and her research group conduct low-energy ion-radical molecule collision dynamics experiments to probe the reactivity of these species. These experiments mimic the conditions in the low-temperature environment of the interstellar medium. Preliminary experiments investigate the reactions of hydrogen and nitric oxide with calcium(+) ions (in a variety of electronic states) cooled in an ion trap. In the most ambitious experiments, the reactions between very slow radical molecules and cooled and trapped molecular ions are studied. The radicals (OH, CH, NH) are created in a molecular beam by laser-photolysis or via pulsed discharge. These radicals are slowed with a series of decelerator electrodes using a new type of continuous-wave decelerator developed in the Lewandowski laboratory. The slowed molecules enter an ion trap (e.g. a linear Paul trap), where they interact with a population of cooled ions. Diagnostics are performed (optical imaging of the ions, destructive time-of-flight mass spectrometry of products, etc.) Ions to be studied include the following: singly-ionized species: acetylene, ammonia, methane, hydroxyl (OH+), and methylidyne (CH+). The Lewandowski research group includes active involvement by undergraduates in authentic research. In addition to her experimental work, Prof. Lewandowski works with ALPhA and postdoctoral fellows from the Physics Education group at University of Colorado to develop and run a workshop to assist significant numbers of higher-education faculty members in incorporating modeling into the educators' own laboratory curriculum.