Application of isomer-selected spectroscopy by ion-drift tube method to the intracluster reaction products

我们利用最近研制的自制的质量-异构体分离检测系统，成功地分离了具有不同异构体结构的碳簇离子。在该系统中，一个充满氦气的离子漂移管电池位于飞行时间（TOF）质谱仪的无场区域内。在簇源中产生的离子经静电场加速后注入电池。然后，离子在电场的引导下穿过电池，与背景He气体一个接一个地碰撞。我们可以在电池中分离不同结构的离子，因为电池中离子的迁移率取决于离子的几何截面。随着这一体系的发展，我们研究了具有一个以上同分异构体结构且能量相当的气相络合体系。本项目主要做了以下研究：1)镁与甲基卤化物、Mg^+-XCH_3的单离子化光解光谱及动力学研究；2)碘化钠簇离子与醇吸附物的光解光谱研究；3)通过光解质谱和亚稳单分子解离反应的观察，对含碱金属原子与多个丙烯腈分子体系的簇内聚合产物进行结构鉴定。4)氮化硼簇离子B_nN^+的多光子激发解离反应机理及其途径。从这些研究中，我们发现了几种通过激光光谱从多元异构体体系中识别每种异构体结构的方法，以及使用离子漂移管装置的直接分离方法。更广泛的光解动力学和光谱学的气相配合物或团含金属原子的研究正在进行中。

We have succeeded in separating mass-selected carbon cluster ions with different isomer structures, by using a home-made mass-and isomer-separation and detection system developed recently. In this system, an ion-drift tube cell, which is filled with helium gas, were located inside a field-free region of a time-of-flight (TOF) mass spectrometer. Produced ions in a cluster source were injected into the cell after acceleration by static electric fields. Then the ions were guided through the cell by an electric field, colliding with the background He gas one after another. We can separate the ions with different structure in the cell, because the ion mobility in the cell depends on the geometrical cross-section of the ion. Along with the development of this system, we have investigated gas-phase complex systems which have more than one isomer structures with comparable energy. The following studies have been done in this project ; 1)photodissociation spectroscopy and dynamics of magnesium monocation with methyl halide, Mg^+-XCH_3, 2)photodissociation spectroscopy of sodium iodide cluster ions with alcohol adsorbate, 3)structure identification of intracluster polymerization products for the system including an alkali-metal atom with plural acrylonitrile molecules by photoionization mass spectrometry and by the observation of metastable, unimolecular dissociation reactions, and 4)multiphoton excitation and dissociation reaction mechanism and its pathways from boron nitride cluster ions, B_nN^+. From these studies, we have found several ways to identify each isomer structure from plural isomer systems by laser spectroscopy, along with the direct separation method using the ion-drift tube apparatus. More extensive studies of photodissociation dynamics and spectroscopy for the gas-phase complexes or clusters containing metal atoms are now undergoing in our group.