Fast-electron-impact Study On Excitations Of 4d Electron Of Xenon

The energy level structures and dynamics of atoms and molecules are the basic research contents in the atomic and molecular physics. The knowledge of forbidden transitions of atoms and molecules, especially for the inner shell excitations, is relatively scarce. The reason is due to the high excitation energy of the inner-shell state, which is beyond the photon energy of laser. Despite the high energy of the synchrotron radiation, the forbidden transition of inner-shell can not be reached via multi-photon excitation which is widely used in laser spectroscopy. The main reason is due to the lower intensity of synchrotron radiation compared with laser. Considering that the electron collision can excite the dipole-forbidden transitions at large momentum transfer, it provides an unique experimental technique to explore the inner-shell forbidden transitions. This dissertation mainly focuses on the study of forbidden excitations of 4d electron of xenon based on the electron energy loss spectrometer, and the results and innovations are as follow:1. The electron energy loss spectrum of the 4d excitations of xenon was measured at an incident electron energy of 1500 eV and a scattering angle of 6°. The energy position and natural width of the quadrupole-allowed transition of 4d5/2-16s [5/2] 2 are re-ported for the first time. The physical information of the optically forbidden transitions of 4d5/2-1ns,4d5/2-1nd, 4d3/2-12ns’ and 4d3/2-12nd’ were reported at the same time. It is found that the natural widths of both the quadrupole-allowed transition of 4d5/2-16s[5/2]2 and the natural widths of the dipole-allowed ones are nearly identical and independent of the main quantum number n within the experimental errors. In addition, the present natural widths are in general agreement with the recent synchrotron radiation ones. The above phenomena may be due to that the spectator transitions dominate the resonant Auger effect for both dipole-allowed and dipole-forbidden transitions.2. In order to improve the resolution of the electron collision, we designed the new Ultra High Resolution Electron-Energy-Loss Spectrometer. The low pass energy and tandem analyzer are used in the spectrometer, which decline the background of the experiment and improve the profile of instrumental function and enable the resolution to reach 10 meV. The new retarding lens system, tandem analyzer system and detection system are introduced in this dissertation. The new designed retarding lens can adjust the electron beam energy over a wide range. The manufacture of the spectrometer has been completed and is under adjusting at present.