Electron Momentum Spectroscopy Study Of Heavy Elements Systems

Electron momentum spectroscopy (EMS), with a history near 40 years, has been a powerful tool for investigating of electronic structure, electronic correlation effects and ionization mechanism in matters. EMS can directly measure the electron energy and momentum density distributions of matter, and its application has been extend to the fields of physics, chemistry, and biology. With the improvement of energy and momentum resolutions, electron momentum spectrometer can study some new and valuable areas, which were very difficult in past. In addition, the rapidly developed relativistic quantum chemistry theory has made possible the EMS study of heavy elements systems.The main goal of this thesis is to combine the relativistic quantum chemistry calculation with EMS experiments to study valence electronic structures of heavy elements system. The combination of relativistic quantum chemistry and EMS is a new research area. There was no experience can be used for reference, therefore this area is full of difficulties and challenges.After learning how to use the relativistic quantum chemistry program ADF, an interface program was successfully complied to generate theoretical momentum distributions from the standard ADF output file, which made EMS study extend to the systems containing heavy elements. This program will be very helpful for our laboratory future development.The relativistic effects in the outer valence p orbital of Xenon and Krypton were investigated using high resolution EMS experiments incooperating with relativistic chemisty calculations. The comparions of non-relativistic and relativistic theoretical momentum profile revealed that the relativistic effects have remarkable influences on the electron density distributions of diatomic molecules I₂ and Au₂.The outer valence orbitals of tungsten hexacarbonyl and ferrocene were measured using our third-generation electron momentum spectrometer. Incooperation with non-relativistic and relativistic calculations, the relativistic, distorted-wave and vibrational effects in the outer valence orbitals of these two polyatomic molecules were investigated systematically. Moreover, the experimental electron momentum spectra of 5e_1/2 and 5e_3/2 orbitals of CF₃I were interpreted with relativistic calculations, and relativistic effects in the valence orbital of UF₆ were predicted in theory.