Study Of The Photodetachment Of H~-Ion Near A Sphere Surface

The researches of negative ions have been extended to all areas of peoples’ life. Peoplenot only can accurately measure the electron affinities with the photodetachment method butalso can study the plasma ionization, excitation, and scattering processes. It also plays animportant role in the elastic scattering charge transfer during the molecular collision reaction.People used the method of the numerical simulation to get the same conclusion of theexperiment. Some common negative ions are N2-,H2-, etc. The ground states of thesediatomic molecules are unstable, so the spontaneous desorption phenomena are usually easyto happen. However, the element of hydrogen is weakly negative, its electron affinity is about0.754eV. Therefore, the hydrogen negative ion is stable in nature. So people use the hydrogennegative ion to study the movement of the detached electron and the oscillatory structure ofthe photodetachment cross section in different external environment. During the study, wecomprehensively used the electrostatic image method, the theoretical imaging method andclosed orbit theory to analyze and calculate the oscillatory problems in the photodetachmentcross section. At the same time, we studied the photodetachment ofH-ion near a sphericalsurface in the presence of electric field and got clear and reliable results.The main study of this thesis includes three aspects:1. The photodetachment ofH-ion near an elastic deformed spherical surface or anelastic deformed arc surface has been studied on the basis of the theoretical imaging method.We calculated the detached electron flux distribution and the photodetachment cross-section.The calculation results suggest that the influence of the plane on the photodetachment ofnegative hydrogen ion is limited only in a certain range. In the region closed to the z axis, thespherical effect dominates and the electron flux and photodetachment cross section are thesame as only the sphere surface exists. The influence of the plane can be neglected. But in theregion far from the z axis, both the plane and sphere surface impact. The deformed sphericalsurface has significant effect on the photodetachment process. If we fix the distance betweenthe deform sphere and the hydrogen negative ion, the detached electron flux distributionapproaches the case of only spherical surface exists with the increase of the radius of thesphere.2. We study the photodetachment ofH-ion near a metallic sphere surface on the basis of the semiclassical closed orbit theory and the electrostatic image method. We find out theclosed orbits of this system and put forward a formula for calculating the photodetachmentcross section. The research suggests: the photodetachment cross section is not only related tothe radius of the metallic sphere surface, but also related to the ion-surface distance. As theradius of the metallic sphere surface is increased, the oscillating amplitude of the cross sectionis strengthened. When the radius of the metallic sphere is very large, the cross sectionapproximates the case of the photodetachment ofH-near a metallic flat surface. In addition,the photodetachment of hydrogen negative ion near a deformed metallic sphere surface hasalso been studied. Two cases are studied, one case is the deformed metallic sphere surfaceconnected with the ground; another case is the surface unconnected with the ground.Compared to the case of the photodetachment ofH-near a metallic sphere surface, we findwhen the deformed metallic sphere surface is connected with the ground, the electrostaticpotential caused by the images of the detached electron has strengthened the oscillatingamplitude in the photodetachment cross section; however, when the deformed metallic spheresurface is unconnected with the ground, the oscillating amplitude of the cross-sectionbecomes decreased.3.The control of the photodetachment ofH-near a metallic sphere surface by an elasticinterface or electric field has been studied. Compared with the photodetachment ofH-near ametallic sphere surface, the position of the elastic interface has significant effect on thephotodetachment cross section. The oscillation in the cross section of our system becomesstrengthened with the decrease of the distance from the elastic interface to H-ion. In addition,our calculation results suggest that the influence of the elastic interface becomes much moresignificant when it located in the lower half space rather than in the upper half space. Whenthe external electric field is along the+z axis, the oscillatory structure in the photodetachmentcross section becomes strengthened. Therefore, we can use the elastic surface and the externalfields to control the photodetachment ofH-ion near a metallic sphere surface.Through this study, people may have a new understanding on the photodetachmentprocess of negative ion near surfaces. Our study may guide the future experiment research onthe photodetachment microscopy. Using the semiclassical closed orbit theory to study thephotodetachment of hydrogen negative ion near different surfaces is of great significance to enrich and develop this theory. Our study has important application prospect in plasmaphysics, surface physics, etc.This thesis is divided into five chapters. The first chapter is the introduction, whichintroduces the research significance of the photodetahcment of negative ions, the domesticand overseas research status and the innovation points of this thesis. In chapter two, weinvestigate the photodetachment ofH-ion near an elastic deformed spherical surface or anelastic deformed arc surface on the basis of the theoretical imaging method. In chapter three,we study the photodetachment ofH-ion near a metallic sphere surface and a deformedmetallic sphere surface based on the closed orbit theory, especially discuss the cases when thedeformed metallic sphere surface connected or unconnected with the ground. In chapter four,we study the control of elastic interface and the electric field on the photodetachment ofH-near a metallic sphere surface. Some conclusions and prospects are given in chapter five.