The Potential Energy Functions Of SiO Molecule And The External Electric Field Effects On SiO_x(X=1,2) Molecules

The molecular potential energy function is the theoretical foundations of studying theoretical chemistry and atomic and molecular physics. Educing the potential energy function of diatomic molecule from theoretical computation, especially the potential energy function of the excited states of diatomic molecule, is one of the important researches for atomic and molecular physics at all times. On the one hand, the potential energy function is the whole description of the geometrical and electronic structure of molecule, on the other hand, diatomic molecular potential energy function is the foundation of structuring the entire space potential energy function for polyatomic molecule, the key of investigating atomic and molecular collision and molecular reaction dynamics, and the basis of molecular stability.The investigation on the properties of molecule under external field has become one rising research field. Studying the reaction between molecule and external field and the physical and chemic change under external field are very important for realising excitation properties and aging mechanism of material. Theoretical computation is mainly the properties for the ground state of atom and molecule, such as the geometrical structure of molecule, energy, dipole moment and so on. The excited states under electric field have been regarded in recent years, but the theoretical investigation is lag. Therefore the investigation on atom and molecule under external field, especially the investigation on the excited states under strong external field, is the important work for many domains, and has important theoretical and applied values.In this paper, the structure optimization computation for the ground and excited states of SiO molecule is carried out using density functional theory B3P86 method, SAC-CI method and different basis sets in Gaussian03 program package, then the potential energy is scanned, the Murrell-Sorbie function is fitted and the force constants and spectroscopic constants are calculated, the calculations here provide useful potential energy function for the molecular reaction dynamics of SiO system. The calculations of transition wavelengths, oscillator strength, Einstein coefficients of SiO and SiO₂ molecules from ground state to the first five different excited states are calculated by employing CIS-DFT method. At the same time, the geometrical structure of ground state, electric dipole moment, HOMO, LUMO, energy gap, excited energy and energy level for SiO and SiO₂ molecules under different external electric field are optimized. Then the transition wavelength and oscillator strength for the excited states of SiO and SiO₂ molecules under different external electric field are investigated. These provide a certain of theoretical foundations for the excitation properties of SiO and SiO₂ molecules.In this paper, Chapter 1 describes the investigation background, methods and contents; Chapter 2 describes the basic theories of the potential energy function and the excited states under the external electric field; Chapter 3 studies the potential energy functions for the ground and excited states of SiO molecule; Chapter 4 studies the external electric field effects on SiO molecule; Chapter 5 studies the external electric field effects on SiO₂ molecule; at last, the conclusions are given.