Development of the Cold Collision Electron Spectroscopy

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The scattering of very low energy electrons by atomic and molecular targets are expected to be strongly dominated by quantum effects involving phenomena such as quantum interference and revealing new and unexpected behavior. Recently, experimental technique for measuring the total cross section of the electron molecule collisions at very low energy of below a few hundred meV was developed. Mono-energetic photoelectrons produced in the near-threshold photoionization of atoms by monochromatized Synchrotron Radiation (SR) were used as a source in their technique. This technique made it possible to produce very low energy electron beam, even below the energy of〜40 meV, which corresponds to the room temperature. In their setup, however, the energy width of the electron beam depends on the spot size and the band width of the monochromatized SR, which are trade-off between the photon flux of the excitation photon beam. Therefore, highly brilliant incident photon beam was necessary. In the present research, we developed a new experimental technique Cold Collision experiment utilizing the SR with much highly efficiency.The key of the present technique is to use the penetration field to correct only the "0" energy photoelectrons, instead of applying the constant filed across the photoionization region. Under high resolution photon beam conditions, threshold peaks are asymmetric, characterized by a sharp rise and a more slow fall off in the high energy side. The slow fall off corresponds to energetic or 'hot' electrons that are emitted from the interaction region directly into the electron lens. The high energy tail can be reduced by appropriate potentials in the second stage of the optics. We successfully obtained the total electron scattering cross sections of Xe by the beam attenuation method with our new setup.