This thesis presents a theoretical investigation of ultrafast dynamics during strong laser field ionization with atoms and molecules.
For that a new method for solving the time-dependent Schrödinger equation was developed and implemented, where a hybrid discretization was used with cylindrical coordinates with a finite element method for the radial coordinate and a pseudo-spectral technique for the axis coordinate. The main results of the thesis are:
1). Orientation dependence, orbital symmetry dependence of molecular field ionization was studied with a two-dimensional model molecule. To get the information of rescattering electrons, an analytical probing of rescattering electrons was implemented. By studying the momentum distribution of rescattering electrons during strong field ionization of molecules, we found that the rescattering process is strongly dependent on the orientation and symmetry of the molecule. 2). Sub-cycle dynamics during laser field ionization of molecules was investigated. With a two-dimensional diatomic molecule model, we found that the laser induces sub-laser-cycle dynamics during field ionization and the field-induced sub-cycle dynamics modifies the time structure of rescattering electrons. Such dynamics may modify the time-frequency structure of high-order harmonic response, or lead to the appearance of even harmonics with certain laser intensities. 3). An extreme-ultraviolet (XUV) probing method with attosecond resolution has been applied to study ionization dynamics of a hydrogen atomin a strong infrared laser field. Distortion of ground state and electron excitation during strong field ionization influence the total XUV photon ionization yield. We found the total XUV photon ionization yield follows electron density near the nucleus.