Study On The Photodetachment Of H~- Ion And Photoionization Of H Atom Near A Dielectric Surface

Study of the photodetachment of the negative ions and the photoionization of highly excited atoms in the strong field and near surface is the front research area in atomic and molecular physics, which are typical examples to study the semi-classical theory and quantum chaos. In the previous theoretical studies, peopele mainly study photodetachment of negative hydrogen ion and photoionization hydrogen atom in the external fields and near metal surface, as to the photodetachment of negative hydrogen ion and photoionization of hydrogen atom near dielectric surface, the reports are relativley little. With the development of semiclassical theory, photodetachment and photoionization microscopy image technique, which are effective methods to observe the oscillation structure of wave function in macroscopic scale have relatively mature theoretical researches, at the same time, in the experimental aspects, there are many researches about the photodetachment and photoionization microscopy. When a laser light irradiates on a negative ion or an atom, the electron may absorb photon energy and excite from a low-energy bound state to higher excited states. The electron propagates outward in the form of electronic wave. Under the influence of the external fields and the surfaces, the electrons travel along different trajectories may arrive at a given point on the detector plane. The interference of the electron waves induces the oscillatory structure in the interference pattern on the detector plane.In this paper, by using the semiclassical theory in combination with the electrostatic imaging method, we study the influence of the dielectric sphere surface on the photodetachment of H~- ion, the influence of the dielectric surface and magnetic field on photoionization microscopy of H atom. Using the semi-classical theory to study the photodetachment of negative hydrogen ion and photoionization of highly excited atom near surfaces is not only vital to enrich and develop the theory itself, but also has great application prospects in high-tech fields, such as in plasma physics, ion trap, the design and development of the photoionization microscopy,etc.The main research of this thesis includes three aspects:1. The photodetachment of hydrogen negative ion near a dielectric sphere has been studied by using the electrostatic image method combined with the semiclassical closed orbit theory. Firstly, we analyze the image charge distribution of the detached electron near the dielectric sphere; then we put forward the Hamiltonian of this system. By solving the Hamiltonian canonical equations, we search out the closed orbits of the detached electron. Then we calculate the action and period of the closed orbits and derive the formula for the photodetachment cross section. Finally, we analyze the influence of the dielectric sphere on the oscillatory structure of the photodetachment cross section. The calculation results suggest: the oscillating amplitude in the photodetachment cross section of hydrogen negative ion near a dielectric sphere is decreased with the increase of the photon energy. With the increase of the dielectric constant, the oscillation in the photodetachment cross section becomes stronger and the region of the energy in the oscillating structures becomes increased.2. Based on the semiclassical open-orbit theory, we study the influence of the dielectric surface on the photoionization microscopy of hydrogen atom. First of all, we establish a schematic plot of the hydrogen atom and its electrostatic image near a dielectric surface. Through a scaled transformation and coordinate transformation, we obtain the Hamiltonian of the high excited hydrogen atom near the dielectric surface. Then we simulate the trajectory of electrons by numerical calculation, calculate and analyze the electronic probability density distribution on the detector plane. Finally, by changing the dielectric constant and the scaled energy, we can control the photoionization microscopy of hydrogen atom. According to this research we find, at a given dielectric surface, with the increase of the scale energy, more types of electronic orbits appear on the detector plane, and the electron probability density exhibits more complex oscillation structure. At the same scale energy, the dielectric constant also has a significant effect on the electron probability density on the detector plane. With the increase of the dielectric constant, chaos appears and more types of electron ionization trajectories appear, which makes the interference patterns in the electron probability density distribution get more complex.3. We study the regulation of the magnetic field on the photoionization microscopy of the hydrogen atom near the dielectric plane. Firstly, the dynamic properties of the electron in the presence of the dielectric surface and the magnetic field are studied, and the Hamiltonian of this system is given using the method of electrostatic imaging method. By solving the Hamiltonian motion equation, we find the electron trajectory arrived at a given point on the detector plane. Based on the semiclassical theory, the formula for calculating the electron probability density is derived, and the oscillation structure of the electronic probability density is calculated and analyzed. Especially, we study the effect of magnetic field on the photoionization microscopy of the hydrogen atom near the dielectric plane, and compare the calculation results with the case of the photoionization microscopy near the dielectric surface without magnetic field. Then we research the oscillation of the radial electron probability density distribution on the detector plane by changing the magnetic field strength, the scaled energy and the dielectric constant. Our research results suggest: for a given dielectric surface, with the increase of the magnetic field strength, the change of the interference pattern on the detector plane is divided into two processes. Firstly, when the magnetic field strength is less than an intermediate value, with the increase of magnetic field strength, the number of the electron trajectories is decreased. When the magnetic field strength is equal to this intermediate value, only direct electron trajectories have contribution to the electron probability density distribution and the oscillation is very weak. Then when the magnetic field strength is larger than the intermediate value, with the increase of magnetic field strength, more complicated indirect trajectories for the excited electron will appear and the oscillation in the electron probability density distribution becomes increased. At a given scaled energy and magnetic field strength, the electronic probability density distribution on the detector plane can also be affected by the dielectric constant. With the increase of the dielectric constant, chaos disappears and more types of indirect electron ionization trajectories disappear, which makes the interference patterns in the electron probability density distribution get simple.Through the study of this paper, the effect of dielectric surface to the photodetachment of H~- ion and photoionization microscopy of H atom can be more clearly. This stduy can deepen people’s understanding of the photodetachment of negative ion and the photoionization microscopy of highly excited atom near dielectric surfaces, and can provide some reference values and theoretical guidance for the experimental exploration and application of photodetachment microscopy and photoionization microscopy of the ions or atoms near the surfaces.This paper is divided into five chapters. The first chapter is introduction, we mainly introduces the semiclassical theory, the domestic and foreign research status and significance of the topic and the innovation of this paper. The second chapter is the study on the influence of dielectric sphere to photodetachment of H~- ion based on the image method and the semiclassical closed orbit theory. The third chapter studies the photoionization microscopy of hydrogen atoms near the dielectric surface using the semiclassical open-orbit theory. The fourth chapter is the regulation of the photoionization microscopy hydrogen atom near the dielectric plane in the case of the external magnetic field. The fifth chapter gives the conclusion of this paper and the prospect of the related research.