Cold Controlled Reactions between Molecular Ions and Radicals

在这个奖项，由化学系的化学结构，动力学和机制（CSDM-A）计划资助，科罗拉多大学的石楠Lewandowski教授和她的研究生和本科生同事正在研究稳定和反应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星际介质（ISM）中的环境。 制备具有这些低能量的孤立离子和/或分子的困难已经排除了任何重要的实验工作来研究ISM中的化学;这一研究领域实际上是一个未知的前沿。 像这样的研究可以引导人们了解ISM中可以发生什么样的化学反应，并作为低能碰撞过程计算模型的非常敏感的检查。 在Lewandowski小组工作的学生接受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。 Lewandowski教授和她的研究小组还参与了与高级实验室物理协会（ALPhA）合作的一项计划，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所在机构的现有实验中开发基于建模的方法。石楠·Lewandowski教授和她的研究小组进行了低能离子-离子自由基分子碰撞动力学实验，以探测这些物种的反应性。 这些实验模拟了星际介质的低温环境条件。 初步实验研究了氢和一氧化氮与在离子阱中冷却的钙（+）离子（各种电子态）的反应。 在最雄心勃勃的实验中，研究了非常缓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。 这些自由基被一系列减速器电极减慢，减速器电极使用Lewandowski实验室开发的新型连续波减速器。 减慢的分子进入离子阱（例如线性保罗阱），在那里它们与冷却的离子群相互作用。 进行诊断（离子的光学成像、产物的破坏性飞行时间质谱等） 待研究的离子包括以下：单电离物质：乙炔、氨、甲烷、羟基（OH+）和次甲基（CH+）。 Lewandowski研究小组包括本科生积极参与真实研究。 除了她的实验工作，教授Lewandowski与ALPhA和博士后研究员从物理教育组在科罗拉多大学开发和运行一个研讨会，以协助大量的高等教育教师在纳入建模到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.