Electron correlation multi Auger electron emission from hollow atoms

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Multi-electronic excited states which are produced by multi-electron capture reaction of highly charged ions in collisions with neutral molecules are known as hollow atoms because their inner shells have vacancies while the outer shells have occupied by a lot of electrons. If kinetic energies and ejected angles of more than two Auger electrons which are ejected from the hollow atom at the same time are measured, we can regard the experimental result as the direct observation the electron correlation effect. In order to obtain a wide solid angle and sufficient energy resolution, we have chosen the combination of a magnetic-trap-type drift tube with weak magnetic field and a two-dimensional position sensitive detector. A detector which can be used in the magnetic field and has high speed response is necessary for this experimental setup. We have contrived a new detector which using a resistive film anode combined with a modified backgammon with weighted capacitors readout pad and have developed it successfully. In time of-flight measurements using a high-speed digital oscilloscope, we have achieved a very good time resolution of less than 1 ns by the developing of a new algorithm for analysis of time spectra. Highly charged ions are provided by an electron cyclotron resonance ion source in Tokyo Metropolitan University. For the time-of-flight measurements, the ion beam is chopped by an electric pulse applied to an electrode. As a target gas, we have prepared a supersonic molecular beam for obtaining good time and spatial resolutions. Finally we have constructed an apparatus for the multi-Auger electron spectroscopy with the combination of some devices described above. In this setup, the charge of ions after both of the electron capture and the electron emission should be analyzed for the coincidence measurements with the ejected electrons which give us the information about the electronic states of the hollow atoms.