Appliction Of One Particle Green Function To Electron Momentum Spectroscopy

Electron momentum spectroscopy (EMS), which can give both of the electron binding energies and the electron momentum density distributions at the same time, has been developed to be a powerful tool for the investigation of electronic structures, electronic correlation effects and electron ionization mechanics. It has extensive applications in the fields of physics, chemistry and biology. With the newly constructed third generation electron momentum spectrometer, which features high efficiency and high resolution, some new and valuable studies, which were very difficult in past, now become possible.This thesis mainly includes two parts: one is the interpretion of electron momentum spectra of valence molecular orbitals using one particle Green's function method (1p-GF), the other is the investigation of electron density distribution in momentum space for core shells of molecules containing two equivalent atoms.The conformations of dimethoxymethane and n-pentane have been probed with Focal Point Analysis, one particle Green's function and EMS. It has been exhibited that EMS has unexploited potential in experimentally studying conformation of versatile molecule, can image anomeric effects in dimethoxymethane, distortions and topological changes that molecular orbitals undergo under internal rotations and variations of forms of n-pentane in momentum space.Exhaustive EMS studies on thiophene and cyclopentene have been carried out with one particle Green's function. Comparison between theoretical electron momentum distributions and experimental results confirms that outer and inner valence orbitals of two unsaturated ring molecules are both subject to breakdown of one electron picture of ionization, shows that, besides distortion effects, vibronic coupling probably results in the difference between experimental data and theoretical predictions at low momentum region in d-like orbitals, which are beyond Born-Oppenheimer plane wave impulse approximation, and moreover images through spaceσ-conjugations electronic interaction.The investigation of core states having two equivalent atoms have been presented. The momentum density maps of these core molecular orbitals exhibit periodical oscillation due to the interference effects of the equivalent atoms. Therefore, EMS can provide direct information on the nature of the nuclei geometry and orientation by investigating core states.