Full Angle (e, 2e) Electron Momentum Spectrometer Developed And A Number Of Molecular Electronic Structure Study

This thesis presents my main research work as a Ph.D.candidate,which includes two parts:Part One mainly discusses the development of a high-coincidence-count 2Ï€(e,2e) spectrometer which employs a series of key experimental techniques.This part includes four chapters as the following.In the first chapter,the principle of(e,2e) reaction,theoretical background, experimental arrangements,and the recent research progress of electron momentum spectroscopy(EMS) have been introduced.In the second chapter,the spectrometer has been described in detail.The different components of the spectrometer are respectively introduced,which includes the electron gun,a series of electron optical lens system,gas cell,analyzer,vacuum system,power supplies system,etc.In the third chapter,the key component of the spectrometer,a position sensitive detector(PSD) with a two-semicircle wedge and strip anode and multi-parameter data acquisition system have been designed and presented,which include the principle and facture of wedge and strip anode,output and process of signals from PSD,and experimental data acquisition.In addition,the performance of the two-dimensional PSD has been tested.The modulation effect has been simulated and the results are compared with the experiments.In the fourth chapter,the ways of adjustment and performance test of the spectrometer have been expatiated.The performance of the 90°sector energy analyzer has been tested by elastic scattering.The results show that the energy resolution of the analyzer is about 1.5 eV at passing energy of 600 eV.Moreover,at the incident electron energy of E₀= 1217 eV,the(e,2e) coincident time spectrum for Ar 3p ionization has been obtained.The time resolution is approximately 7 ns(FWHM).At the same time,the binding energy spectrum for Ar 3p orbital has also been measured. The energy resolution is approximately 2.1 eV(FWHM).The relative azimuth angle range of±130°for simultaneous detection has been achieve,which covers almost 2Ï€angles.Part Two discusses the EMS study on dibromodifluoromethane(CF₂Br₂) and ab initio calculation studies on 2-aminoethanol(NH₂C₂H₄OH) and N,N-dimethylaminoethanol(N(CH₃)₂C₂H₄OH).This part includes four chapters as the following.In the fifth chapter,the basic theoretical backfround used in this part is introduced including Hartree-Fock(HF) theory,density functional theory(DFT) and natural bond orbital(NBO) theory.In the sixth chapter,the measured electron momentum profiles of valence orbitals of CF₂Br₂ are compared with Hartree-Fock(HF) and density functional theory(DFT) calculations with different-sized basis sets.In general,the DFT-B3LYP calculation using the large basis sets of 6-311++G^** and aug-cc-pVYZ fairly describe the experimental results.Moreover,the controversial orderings of the outer valence orbitals have been reassigned.The pole strength of the main ionization transition from the inner valence orbital of lb₂ is determined.In the seventh and the eighth chapters,thirteen low-lying conformers of 2-aminoethanol(AE) and twelve low-lying conformers of N,N-dimethylaminoethanol (DMAE) are investigated using the density function theory(DFT) and M3/411er-Plesset perturbation theory calculations methods.The geometries and energies of all conformers are discussed.At the same time,the predicted IEs of low-lying conformers are used to assign the two lowest ionization bands in PES and to interpret the reason why the ionization bands moving with the temperature.Natural bond orbital(NBO) analyses exhibit a remarkable influence on the molecular electronic structures by the strong intramolecular HB OH…N and the relative weak intramolecular HB NH…O,leading to the significantly lowered energy levels of the occupied lone-pair molecular orbitals.