Cwdvr Spectral Method And Its Application In The Strong Field Atomic Physics

"Numerical experiment" is one of the most important approaches in strong field physics, which has been proved to be very flexible and realistic enough to give valuable physical insight. In this thesis, we present an accurate and effective the coulomb wave function discrete variable representation (CWDVR) pseudospectral method for solving the three dimensions time-dependent Schrodinger equation (TDSE) involving the Coulomb potential. The new algorithm, which can be used to simulate the quantum dynamics in complex electromagnetic fields, will be found more efficient than the close-coupled wave packet method and methods based on evenly spaced grids. For examples, we apply the CWDVR generalized pseudospectral method to study the High-order Harmonic Generation (HHG) and ionization dynamics of a hydrogen atom interacting with strong laser pulses. In addition, a simple and highly accurate method has been developed in this thesis, which based on the CWDVR generalized pseudospectral discretization for investigating the behavior of atomic system in strong magnetic field. The thesis is divided into four parts.The first part of this thesis, consisting of Chapter 1 and 2, is an introduction of the physical background and fundamental theories. Chapter 1 introduces the general physics of light-matter interactions, in particular, the interaction of intense laser with atoms. A brief review on the calculations of a hydrogen atom in a strong magnetic field is also given in this chapter.The next fundamental chapter is devoted to the non-relativistic time-dependent Schrodinger equation (TDSE). At first, we review some basic properties of the TDSE and some general ways to solve this equation. In the following, the steps of the implementation of the CWDVR spectral method are considered in detail. Finally, calculations on bound state energies, expectation values and radial moments and so on for different atomic potential are presented, respectively, to demonstrate the accuracy of the present method.The second part of the thesis, starting with chapter 3, is devoted to the study of ionization dynamics with different electromagnetic radiation sources, ranging from weak non-coherent electromagnetic field to strong laser field. Calculations on the photo-absorption strength of hydrogen atom are presented to demonstrate the accuracy of present method in low energy limit by the time-dependent wave-packet propagation method. As another example, the present method is applied to multiphoton ionization of H atom. For a wide range of field parameters, ionization rates calculated using the present method are in excellent agreement with those from other accurate theoretical calculations. The roles of the Coulomb singularity and the long-range potential in above threshold ionization of H atom are also studied with different laser parameters. Furthermore, we analyze the features of the spectra of photoelectrons produced in ionization of the hydrogen atom carefully and give some reasonable explains to the positions and the intensity of resonance peaks in low energy regime.The third part contains the theoretical study of high harmonic generation (HHG) from atoms driven by an intense, femtosecond laser pulse in chapter 4. Firstly, the HHG spectra from different soft-core potential and Debye-Huckel potential are compared to the 3D Coulomb potential. Secondly, we present numerical studies of the HHG from H/He+initially in single bound state (1s,2s,2po or 2p1) or in a coherent superposition state. The analysis reveals that bound-state population and the interference of different channels play crucial roles in determining the conversion efficiency and the form of HHG spectrum. Finally, we propose a method of producing isolated sub-50-as pulse by HHG with a two-color multi-cycle driver laser field theoretically. Our simulations show that the value of the time delay between two lasers can be varied between-0.2 fs and 0.2 fs to keep the isolated sub-50-as pulse generation, which is of advantage to experimental implementation practically.In the final part, based on the CWDVR spectral method, we present the calculations on the binding energies and quadruple moments of the ground and low-lying excited states of the hydrogen atom in a magnetic field strength from zero up to 2.35x109 T in chapter 5. The obtained results are found in excellent agreement with other high accuracy theoretical calculations. The present method may straightforwardly apply to cross electric-magnetic field in arbitrary orientation.