High-precision Theoretical Study Of Fluoride-like Ion Structure And Low-energy Electron-argon Atom Scattering

As the basic unit of matter,the structure of atoms plays a very important role in all research fields of physics.Both the basic energy level structure and transition of atoms and the collision process are the basis of experiment and astrophysics.For example,measurements and studies of atomic structure and collision data can also help determine ion temperatures in tokamaks.Highly charged ions(HCIs)as a special atomic system have been of long-standing interest,not only due to its strong relativistic effect provide many opportunities to explore the basic atomic physics,but also,they have important applications in high-temperature plasma and astrophysics.Optical transitions of many HCIs are sensitive to the fine-structure constant variation and interactions with dark matter,and they can also be used to build high-accuracy atomic clocks.Meanwhile,for the collision process,scattering cross section is the basic parameters required in many fields,while how to deal with the complex multi-body interaction in the scattering process is also a major challenge to the basic theory.Especially for noble gas atoms,its stable closed shell structure provides an ideal model for theory,and the reliable data for electron scattering from noble gases are of crucial importance in applications such as electrondriven processes in phenomena of the radiation chemistry,gaseous discharges,plasmas,and so on.Based on its important applications in laboratory plasma and astrophysics,in this thesis,large-scale B-spline relativistic configuration interaction calculations are carried out to generate the atomic properties of F-like ions of high accuracy using the package Ambit code by Kahl?Berengut.The radial parts of one-electron Dirac orbitals are obtained from the relativistic self-consistent field procedure in which the Breit interaction and QED corrections(vacuum polarization and self-energy terms)are also included.A numerical method is adopted to decrease the size of CI matrix significantly without loss of much accuracy.Energy levels and line strengths for electric-dipole(E1),electricquadrupole(E2),and magnetic-dipole(M1)transitions are provided for the 250 lowest levels of each system.In addition,a detailed analysis is also carried out to explore the convergence and uncertainties of our results.On the other hand,these methods developed to deal with the atom structure with high accuracy can also be applied in low energy electron and positron scattering with atoms.As an example,we carry out a comprehensive study for the electron scattering with atomic argon in the framework of relativistic boxvariational method.The phase shifts first are extracted from relativistic coupled cluster theory calculations,which is possibly the most accurate theoretical method in the calculations for the structure of atom with one or two valence electrons.Then the properties including integrated cross sections and differential cross sections are evaluated and compared with available experimental and theoretical data.The validity and accuracy of present method are verified by the good agreement with experimental values.This indicates that the complex dynamic correlation effect between electrons has a great influence on the accuracy of the results.By taking both linear and nonlinear terms into account in the single-and double excitation coupled cluster calculations,our results show the best agreement with experiments.This thesis includes the following six parts.The first part is an introduction to the development of atomic structure and scattering theory,giving a sketch of the current research status and recent achievements in this field.In the second part,the related theoretical method of atomic structure calculation is introduced with a discussion about how to save computing resources.In the third part,the basic framework of scattering theory and the box-variational method we used are presented,along with the formulations to get the differential cross section,total cross section and momentum transfer cross section.In the part of results and discussion,we report the results of fluorine-like highly charged ions with Z=20-30 generated by the configuration interaction method,including the energy level and transition matrix elements in the fourth part,and also presented a discussion about the uncertainty of our calculations.In the fifth part,we carry out a comprehensive study for the electron scattering with argon.The results of differential and integral cross sections are compared with existing researches.The sixth part systematically summarizes the work of this thesis,and makes a simple outlook on extending this research to higher energy regions and more complex systems.