Ion-Molecule Reactions at Variable Temperatures Using a Molecular Beam-Cold Ion Trap: Radiative association, isomerization and reactions of polar molecules

亚利桑那大学的马克·史密斯得到实验物理化学计划和银河天文学计划的支持，研究离子分子反应速率系数，这些系数对基本反应机制和宽温度范围（4- 800 K）内自然复杂的化学环境都很重要。 将构建采用中性分子束的下一代变温多极阱质谱仪，允许a）捕获离子的多个反应探针，包括使捕获离子与低速、可冷凝物质的密集分子束相互作用以及化学探针反应产物的能力，B）使用脉冲试剂气体/缓冲气体碰撞冷却原位合成复合分子离子，用于随后的射束种类速率测量，以及c）使用其它技术的未来研究，例如离子的状态选择激光泵浦和中性束的速度选择。发达的化学探测和离子包控制将允许在明确的碰撞条件下进行反应和产物研究。 具体项目包括研究烃阳离子在低温下的气相氢化、研究与星际介质有关的HOC阳离子以及探索辐射缔合产物的结构。 这些结果将允许在广泛的能量条件下精确确定反应性和机制，预计结果将导致对反应机制，化学异构化，同位素分馏和能量转移的新见解。这项研究有望改善低温反应动力学的基础以及天体化学实验室研究，加强国际合作。 固有的跨学科计划将有助于培养一些下一代科学家进入这一新兴领域，并有利于亚利桑那大学天体化学的发展。

Mark Smith of the University of Arizona is supported by the Experimental Physical Chemistry Program and Galactic Astronomy Program to study ion-molecule reaction rate coefficients of importance to both fundamental reaction mechanisms and naturally complex chemical environments over a wide temperature range (4-800K). A next generation variable temperature multipole trap mass spectrometer employing neutral molecular beams will be constructed, allowing for a) multiple reaction probes of trapped ions including the capability to interact trapped ions with a low velocity, dense molecular beams of condensable species and to chemically probe reaction products, b) in situ synthesis of complex molecular ions using pulsed reagent gas/buffer gas collisional cooling for subsequent beam species rate measurements, and c) future studies using other techniques such as state-selected laser pumping of ions and velocity selection of neutral beams. Well-developed chemical probing and ion packet control will allow reaction and product studies under unambiguous collision conditions. Specific projects include studies of gas phase hydrogenation of hydrocarbon cations at low temperatures, studies of the HOC cation relevant to the interstellar medium, and exploration of the structure of radiative association products. The results will allow for precise determination of reactivity and mechanism under a wide range of energy conditions, and outcomes are expected lead to new insights into reaction mechanisms, chemical isomerization, isotopic fractionation, and energy transfer. This research is expected to improve the foundation of low temperature reaction dynamics as well as astrochemical laboratory studies, enhancing international collaboration. The inherently interdisciplinary program will help to develop some of the next generation of scientists to move into this emerging area, and benefit the growth of astrochemistry at the University of Arizona.