Photodissociation Studies of Mass-Selected Solvated Cluster Ions

罗切斯特大学的James M.Farrar博士得到了实验物理化学项目的资助，该项目研究气相溶剂化金属阳离子的光解离和裂解。要研究的例子包括碱土金属离子被水、氨或甲醇溶剂化。从对这种在极高真空分子束条件下产生的团簇离子的研究中，可以获得许多关于凝聚相环境中离子分子相互作用的性质的基本信息。在这些非常优雅的实验中，团簇离子是通过从脉冲喷嘴源向溶剂分子的超音速流动中注入低能金属离子而产生的。在质量选择之后，团簇离子被可调谐脉冲染料激光器的光解离，并作为激光波长的函数对子离子进行质量分析。用光学吸收光谱和产物质量谱研究了溶剂化金属阳离子的结构和动力学性质。在这项研究过程中需要研究的具体问题包括：1)吸收光谱随团簇大小的变化，2)溶剂分子的蒸发作为能量耗散机制，以及3)大团簇中分子内电子转移的可能性。这些实验将使用串联飞行时间质谱仪进行，该质谱仪将在赠款期限内建造。

Dr. James M. Farrar, University of Rochester, is supported by a grant from the Experimental Physical Chemistry Program to study the photodissociation and fragmentation of gas phase solvated metal cations. The examples to be studied involve alkaline earth metal ions solvated by either water, ammonia or methanol. From studies of cluster ions of this type, which are produced under very high vacuum molecular beam conditions, much fundamental information can be obtained regarding the nature of ion molecule interactions in condensed phase environments. In these very elegant experiments, the cluster ions are produced by injection of low energy metal ions into a supersonic flow of solvent molecules from a pulsed nozzle source. Following mass selection, the cluster ions are dissociated by light from a tunable pulsed dye laser, and the daughter ions are mass analyzed as a function of the laser wavelength. Optical absorption spectra and product mass spectra are used to elucidate structural and dynamical properties of the solvated metal cations. Specific issues to be investigated during the course of this research involve: 1) changes in the absorption spectrum as a function of cluster size, 2) evaporation of solvent molecules as an energy dissipation mechanism, and 3) the possibility of intramolecular electron transfer in large clusters. The experiments will be performed using a tandem time of flight mass spectrometer which will be constructed during the term of the grant.