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

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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.