Kinetics of Gas-Phase Ion Association and Dissociation

在化学学部实验物理化学项目中，凯斯西储大学的Robert Dunbar将使用离子回旋共振离子阱研究气相离子与激光相互作用的特性。“中型到大型”碳氢化合物、有机金属化合物、簇和复合离子是研究的目标。时间分辨光解动力学，激发离子辐射冷却速率的测量，红外多光子离解动力学，辐射结合效率的测定和复合离子离解产物中振动能量的分配都将被检查。其中一些过程的温度依赖性将使用冷却到77 K的离子阱来确定。将与精通统计力学的专家一起进行红外多光子解离和辐射关联的理论研究。离子回旋共振光谱学技术的发展使科学家们能够捕获带电的原子或分子，即离子，时间相对较长，数量级为秒或更长。有了如此长的存储时间，现在可以更容易地研究涉及离子的各种过程，这些过程可以持续长达几秒钟的时间。这类过程的例子包括吸收光后离子的分裂，其能量刚好足以切断原子间的键（近阈值光解作用），以及红外辐射的发射。邓巴教授的工作将使他能够研究各种相当大的分子离子的几种“缓慢”化学过程。

In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Robert Dunbar of Case Western Reserve University will study the properties of gas-phase ions interacting with laser light using an ion cyclotron resonance ion trap. "Medium-to-large" hydrocarbons, organometallic compounds, clusters, and complex ions are targets for study. Time-resolved photodissociation kinetics, measurement of radiative cooling rates of excited ions, infrared multiphoton dissociation kinetics, the determination of radiative association efficiencies and of partitioning of vibrational energy in the products of complex ion dissociation will all be examined. The temperature dependence of some of these processes will be determined using an ion trap cooled to 77 K. Theoretical studies will be conducted dealing with infrared multiphoton dissociation and radiative association in conjunction with an expert versed in statistical mechanics. %%% The development of the technique known as Ion Cyclotron Resonance Spectroscopy has enabled scientists to trap electrically charged atoms or molecules, known as ions, for relatively long times, on the order of seconds or longer. With such long storage times, various processes involving ions which last up to seconds in time can now be studied more easily. Examples of such processes include the breakup of an ion after the absorption of light with just enough energy to sever the bonds between atoms (near-threshold photodissociation) and the emission of infrared radiation. Professor Dunbar's work will allow him to study several of these "slow" chemical processes for a variety of fairly large molecular ions.