Chaotic Phenomenon For Autoionization

The phenomenon of autoionization for atoms in external fields has attracted scientists'much attention for many years. Recently, one of emphasized topic is the chaotic properties in autoionization process. Rydberg atom is one of a few available low dimensional systems for understanding quantum chaos, so it become optimal object for theoretically and experimentally studying quantum chaos and is typical example demonstrating classical-quantum correspondence because of its intrinsic quantum property. It can be used as the basic theoretical model for microcavity transport and escape from potential.In the lack of external fields, the complexity of atoms, photo-absorption and autoionization spectrum, at present, we mainly use quantum defect theory and R-matrix method. The works done are only limited to low excited states or near the threshold of ionization. Because of the sensitive dependence on the channel states, when there are external fields, the theories above are not available. The electronic pulse trains of Barium above the Stark saddle point based on the chaotic dynamics are entirety irregular in the time threshold, however, the peak-to-peak spacing is roughly the electronic recurrence time. As a result, we can use semiclassical closed-orbit theory to analyze the dynamics properties of autoionization.Semiclassical closed-orbit theory has been extensively used to explain the photo-absorption spectra of atoms in external fields, and has become an important link to connect classical and quantum theory. It is an important method for studying the quantum manifestations of classical chaos and expanding the conception of chaos. In the past decades, the closed-orbit theory has successfully been applied to study the photo-absorption properties of hydrogen as well as multi-electron atoms in various external fields, such as lithium, sodium, cesium atoms and No molecules. The validity of the closed-orbit theory has been fully confirmed, and the recurrence spectroscopy, scaling property and energy statistics have also been developed. However, when taking the nonhydrogen atoms into account, a theoretical studying is more difficult. The multielectron atoms are quantum atomic systems whose underlying classical dynamics is chaotic induced by ionic core scattering. It is core scattering that leads to new recurrence peaks called combination recurrence, and the number of closed orbits increase rapidly near the fork. Therefore, it is necessary to correct and extend the primitive standard closed-orbit theory to include this affect.In this thesis, we mainly study the chaotic properties of autoionization for lithium atoms in external fields. By using special regions-splitting consistent and iterative method combined together with the quantum defect theory and model potential approach, we present the Hamiltonian in cylindrical coordinates of multielectron atoms in strong external fields. Using electric scaling transformation and the semi-parabolic coordinates and introducing an effective Hamiltonian, we calculate the autoionization rate and initial launch angles as the function of scaled time by integrating the Hamiltonian.First, we calculate the autoionization rate and initial launch angles as the function of scaled time for lithium atoms in electric field at scaled energyε=?1.3, and also calculate the autoionization rate and initial launch angles as the function of scaled time for lithium atoms at different scaled energies (-1.2,-1.4), and find that they dramatically different from each other which reveal the chaotic property that sensitively depending on the initial conditions. This chaos is caused by core scattering. By comparing the results with those of hydrogen under the same conditions, we find that hydrogen atoms cannot have chaotic phenomenon because it is an integrabel system. We prove the important role of core scattering for raising the autoionization pulses of the emission electrons of non-hydrogen atoms. Although the autoionization of lithium atoms in electric field present somewhat similar pulse trains occurring for hydrogen atoms in parallel electric and magnetic fields, the patterns are discrepant and the mechanism for pulse creation is fundamentally different from each other and the former part is the result of core scattering while the latter is caused by applied external magnetic field. So, we study what can changed magnetic field affect the chaos of hydrogen atoms.In order to discern the effect of magnetic field and core scattering, we study the autoionization properties for lithium atoms in parallel electric and magnetic field. We calculate the autoionization rate and initial launch angles as the function of scaled time at scaled energyε=?1.92, its chaotic picture of autoionization is much more complicated than the cases of lithium in the electric field and of hydrogen in parallel external fields, which is the result from contributions of the magnetic field and the core scattering process. By comparing the results with those of lithium in the electric field and those of hydrogen in parallel external fields at the same scaled energy, we can see that autoionization rate under consideration here possessing complicated chaotic behaviors is constructed by two kinds of the chaotic dynamics that corresponds contributions of the magnetic field and the core scattering process, respectively. Also, we can conclude that accounting for the chaotic behaviors in escape electron pulse trains particularly for varying the profile of the ionization plot the magnetic field plays a major role, however the core scattering also is critical for determining the locations of the electron pulse peaks.Our works above are not only the extension and the new application for the closed-orbit theory but also provide a quantitative explanation for the complicated chaotic property in autoionization of the Rydberg non-hydrogen atoms. Moreover, our results possess an important insight for experiment research and would also provide a valid approach for studying chaotic transport and escape.This thesis is divided into five chapters. The first chapter is summarization, which briefly introduces the trait and the progress on the atoms in strong external fields, talking about the phenomenon of photo-absorption and autonionization, the purpose and the significance of the subject we choose and the main work we have done. The second chapter discusses the basic theory we used in this thesis, i.e., the closed orbit theory including core scattering, and we also introduces the model potential and the scaling transformation. In the third chapter we calculate autoionization rate and initial launch angles as the function of scaled time for lithium atoms in the electric field and analyze the phenomenon. The forth chapter presents the calculating results of autoionization rate and initial launch angles as the function of scaled time for lithium atoms in the cases of parallel electric and magnetic fields, and makes detail analyses, moreover, we study what can changed magnetic field affect the chaos of hydrogen atoms. In the last chapter, we briefly summarize the total subject and give an outlook for the future work.