| Research Abstract |
Ionization phenomena in gases, liquids, and solids are generally initiated by the electron ejection, main-tained by the collisions of generated plasma particles, such as electrons and ions, and terminated by the charge clearing reaction, namely, recombination between positive and negative ions or that between positive ions and thermalized electrons. With the increase of pressure, where various applications, such as plasma display panel or atmospheric ozonizer, are developed, the electron-ion recombination changes into the for electrons and cluster ions. The purpose of the present investigation is to develop a new spectroscopic tech-que and to substantiate the dynamics and kinetics of the entitled process in such a phase from a point of view of the dynamics of superexcited molecular clusters temporally generated in recombination.
In order to realize the present purpose, we have built a new apparatus for the merged-beams collision of mass selected cluster ions with mono-energetic electron
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s under the high vacuum condition. The apparatus consists of 1) cluster-ion beam source, 2) time-of-flight mass selector, and 3) trochoidal electron spectrometer. In the cluster-ion beam source, the cluster ions are generated by electron impact ionization of neutral clusters in supersonic expansion from a pulsed gas nozzle and extracted by a pulsed electric field. The cluster-ion beam thus extracted is accelerated by about 5 kV and travels through a 1.2 m drift tube and mass-selected using a time-of-flight technique. We have confirmed mass-selected cluster-ion beams up to Ar_<30> and (CO_22)_<30>. The mass-selected cluster ion beam is collided by a mono-energetic electron beam using a merged beams technique ; the trajectory of mono-energetic electron beam is merged with the mass-selected cluster-ion beam in the trochoidal spectrometer, and estranged from the ion beam after the collision. The energy dispersion of electrons and the control of trajectories are simultaneously carried out with the principle of trochoidal electron motion under an electric and magnetic fields both perpendicular to the electron beam. The typical energy width of mono-energetic electron beam is 80 meV.The performance of the trochoidal electron spectrometer is tested by obtaining the scattering cross sections for Ar and CO_2, which reasonably reproduce the published results. The apparatus for the electron-cluster ion recombination thus constructed is optimized for merged-beams recombination experiments. Less
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