The Relative Flow Technique And It’s Application In The Measurement Of The Dynamic Parameters Of Atoms And Molecules

This work mainly focuses on the relative flow rate technique and its application in the measurement of the dynamic parameters of atoms and molecules. For this purpose, an apparatus which can control the flow rate of different gases with high accuracy has been built. Then the generalized oscillator strength (GOS) of6s excitation of xenon was measured based on this technique. With this technique, we simplify the normal-ization processes and improve the accuracy of the normalization. Besides, the relative flow technique also established an unified normalization standard for the future exper-iments. We also designed a new Ultra High Resolution Electron-Energy-Loss Spec-troscopy (HR-EELS) with several new features. For example, the tandem monochro-mator, three-dimensional adjustable filament, and an apparatus which use the electric field to deflect the electron beam angle.In chapter1, the method of electron-energy-loss spectroscopy is described. Then the basic concepts of the optical, generalized oscillator strengths and the differential cross section are introduced. In addition, the two methods of measuring the generalized oscillator strengths (the general method and the gas mixture method) are introduced.In chapter2, the relative flow technique is introduced. We also measured the gen-eralized oscillator strength (GOS) of6s excitation of xenon with this technique. The present result is in good agreement with the previous ones in the small momentum transfer region, which indicates the validity of the relative flow technique. The mo-mentum transfer dependence behavior of the apparent generalized oscillator strength of the6s excitation on the electron impact energies in the large momentum transfer re-gion shows that the first Born approximation is not reached at an impact energy of500eV. Compared with the calculation based on the Hartree-Fock approximation, the result calculated by the random phase approximation with exchange in which the electron cor-relation effect is taken into account more comprehensively is in better agreement with the experimental result in this work, which means that the electron correlation effect is important for the heavy atoms like Xe.In chapter3, the new Ultra High Resolution Electron-Energy-Loss Spectroscopy is described. This chapter mainly focuses on the designing of the electron gun, the monochromator, and also the accelerating lens. Firstly, the new designed electron gun has a transmission of about5%and the pencil angle of the electron beam is less than5°. The new designed three-dimensional adjustable filament also improves the filament assembly accuracy. Secondly, the new designed tandem monochromator has an inherent resolution of about8.6meV, which is much higher than the present apparatus. Thirdly, the accelerating electronic lens can adjust the electron beam energy over a wide range. And when the pencil angle of the incident beam is less than5°, the pencil angle of the emergent beam can be reduced down to less than1°. Last but not least, the new design of the angle deflection apparatus also avoids the possible mechanic problem.