| The interaction of the femtosecond intense laser field with atom and molecule systems is one of the most active frontiers in current atomic, molecular and optical physics. With the development of laser technology, the shorter and stronger laser has been created and applied in the experimental treatments, which provides a powerful tool for the detection of light-matter interactions. The phenomena uncovered in the experiments have also inspired many efforts of theoretical investigations.In present thesis, the Schrodinger equation, which includes the nuclear rovibrational degrees of freedom, is exactly solved by the time-dependent quantum wave packet method. The works we have done are summarized as follows:(1) Based on the former calculations of the vibrational wave packet, the nuclear rotational degree of freedom is taken into consideration in current work. The codes, which calculated the photoelectron kinetic energy spectrum by using the multi-state model, were programmed and parallelized with OpenMP scheme. Hence, the computational efficiency can be substantially increased in practice. Such codes were applied to the study on the coherent control of multiphoton ionization for the Na2 molecule. The calculated results were consistent with the experimental observations and successfully used to explain a variety of phenomena. It indicated that the duration and phase of the laser pulse played important roles in the process of the multiphoton ionization and the chirped laser field was of benefit to the coherent control. We also investigated the dependence of the photoelectron energy spectrum on the initial rotational state and obtained the information of the molecular orientation on the resonant states.(2) We proposed a theoretical scheme in which the photodissociation of the molecule can be controlled by the interference resulting from the wideness and overlap of the two nuclear wave packets on the same potential energy curve. As a typical model, the dissociation of the HD+ molecule was treated by such approach. In our calculation, taking into account two dissociative channels, HD+→D+H+and HD+→H+D+, the two-dimensional quantum wave packet method in the Born-Oppenheimer representation was employed. The density distribution of the fragments in the coordinate and momentum space and the dependence of the products on the kinetic energy and angle were analyzed. It revealed that the delay time and the relative phase between two laser pulses strongly influenced the interference between the two wave packets and hence controlled the dissociation probabilities and the branching ratio in the two channels.(3) Within single-active electron approximation, the codes, which simulated the high-order harmonic generation (HHG) from the atom and diatomic molecule, were programmed independently based on the time-dependent quantum wave packet method. To the best of our knowledge, this is the first time that the HHG from the Ne atom in the two-color has been investigated by solving its Schrodinger equation. Our calculations showed that in the laser field synthesized by a 5-fs/800-nm fundamental driving pulse and a 12-fs/1600-nm subharmonic controlling pulse, harmonic emission was significantly sensitive to the carrier-envelope phase (CEP) of either the fundamental driving pulse or the subharmonic controlling pulse. When neon atoms were driven by such laser pulses with optimal CEP, the generated high-order harmonic spectrum was a supercontinuum corresponding to a single attosecond pulse. The calculated results were excellently explained in terms of the semiclassical "recollison" model and the time-frequency analysis demonstrated our successful choice of the electronic trajectory. |
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