Nitrous Oxide Molecular Valence Shell Excitation States Of The Generalized Oscillator Strength

This dissertation includes four sections. Firstly, the basic physics conceptions of thefast-electron-energy-loss spectroscopy (EELS) are described. Secondly, cross sections for thevalence shell excitations of nitrous oxide are studied. Thirdly, the inelastic integral crosssections of n1S (n = 2 - 3) and n1P (n = 2 - 6) states of helium are investigated andevaluated systematically. Lastly, the new-build atomic beam source has been described.In chapter 1, the brief descriptions of EELS are presented, and the conceptions ofthe generalized oscillator strengths(GOSs), differential cross sections(DCSs), integral crosssections(ICSs), as well as the experimental method, are introduced. Besides, the dataprocesses of the GOS, DCS and ICS are presented, and the approach of BEf-scaling aredescribed.In chapter 2, the DCS, GOS and ICS for the valence shell excitations of nitrous oxide aremeasured by the high-resolution fast-electron-energy-loss spectrometer at an incident energyof 2500 eV and energy resolution of 100 meV. By comparison the present results with theprevious experimental ones, it is found that the first Born approximation is not satisfiedfor the C~1Πexcitation while it is valid for the D~ 1Σ+ excitation at an incident electronenergy of 200 eV. From view point of molecular group theory, the B1△←X~1Σ~+ transition,which includes both the the dipole-allowed transition component and quadrupole-allowedtransition components, is dominated by the quadrupolar component for most K2 region.In chapter 3, the new-build atomic beam source is more compact and the easy comparedwith the previous one. Besides, the tightness of the atomic beam source is improved, andthe contamination of the metal vapor to the vacuum chamber is reduced.