Chaos And Fractal Dynamics In The Ionization Of Rydberg Atoms

The material structure of the microscopic world and the law of the microscopic movements have been constantly explored.In recent decades,great progresses have been made in the field of ultrafast laser theory as well as experiment.The ionization processes and photo absorption dynamics of Rydberg atoms in strong external static fields make great significance to the development of the ionization,and at the same time,it is also one of the theory models in the quantum chaos.Basing on the closed-orbit theory,we research the fractal dynamics of the ionization of Rydberg atoms in external fields,and we find the characteristics of the ionization of Rydberg atoms and the influencing factors of the chaotic escape of ionized electrons.We study the ionization of helium Rydberg atom in an electric field above the classical ionization threshold within the Semiclassical theory.The results show that the ionization of the helium Rydberg atom in the electric and magnetic field shows chaotic characteristics,and by analyzing the self-similar structures of the ionization electrons of the escape time versus the distribution of the initial launch angle of electrons,it is found that there is chaotic phenomenon above the saddle point energy,and there are also self-similar structures in the escape time plots.And we find that the self-similarity region shifts toward the larger initial launch angles with the decrease of the scaled energy.To further study the self-similar structures in the escape time plots and expand the research method,for the first time,we introduce the fractal approach to describe the chaotic dynamical behavior of the ionization.We obtain the fractal self-similarity structure and connect the fractal structure of the escape time plot to the escape dynamics of ionized electrons,of particular note is that the fractal dimensions are sensitively controlled by the scaled energy and magnetic field and exhibit excellent agreement with the chaotic extent of the ionization systems for helium atoms.We extend our research object to the Rydberg hydrogen atom and the Rydberg lithium atom,and by contrasting the fractal dynamics behavior of different Rydberg atoms under different field conditions,it is shown that the core scattering is the primary factor for the fractal dynamics besides the electric and magnetic field.There are six chapters in this paper.It is mainly related to the study of the self-ionization of the Rydberg atoms in external fields,focusing on the chaotic phenomenon and the fractal dynamics in the ionization mechanism.The organization of the thesis is as follows.In the first chapter,we briefly introduce the development and the related research works of atomic ionization,the purpose and the significance of the subject we choose and the development of the closed orbit theory.The second chapter discusses the basic theory we used in this paper--the closed orbit theory including core scattering,the basic process of photon absorption and the evolution of related wave packets are discussed.And we also introduce the model potential and the scaling transformation.The third chapter mainly introduces the nonlinear dynamics,including the theory of chaos and fractal,and gives the calculation method of fractal research.In the fourth chapter,the fractal phenomena of self-ionization and electron chaotic escape time plots of helium Rydberg atom in the applied electric field are calculated,and the fractal self-similar structure is found.The movement characteristics and regularity of fractal self-similar regions under different scale energy are discussed.And the changes of the closed trajectory at different angles are explored,the characteristics of the chaotic system are further discussed.The fifth chapter focuses on the influencing factors of the self-ionization of the Rydberg atom and the fractal dynamics of the self-ionization.The fractal dimensions of the different Rydberg atoms are calculated and the influencing factors are also discussed.The electronic chaos escape mechanism of the Rydberg atom in the field are discussed quantitatively,which provides a simpler and more effective method for the self-ionization of other more complex multi-electron atoms or molecules in the external field and provides theoretical guidance for the experimental study of ultrafast atomic imaging and manipulation.In the last chapter,we briefly summarize the contents of this paper,as well as the outlook for future research.