Studies On Intense-light Photoionization Of 1D Cluster Model

Atomic, molecular and optical physics (AMO) is an important research filed of fundamental physics. With the rapid development of ultrafast technology, the interaction of intense laser with matter becomes a topic of great scientific interest. As cluster is an intermediate state between molecule and bulk solid, the interaction of intense laser with clusters not only plays an important role in many fields of scientific research but also has some potential applications, in areas such as ultrashort X-ray radiation, generation of high-energy electrons and ions, laser-induced nuclear fusion, etc. Among all the effects produced by laser-cluster interaction, photoionization is an extensively-studied topic.This thesis focuses on numerical simulation of photoionizaiton of linear rare gas atomic chain clusters subjected to intense laser field. The content also involves studies on photoionization of 1D full-dynamic H2+ model, as well as design of Time-of-Flight Mass Spectrometry (TOF-MS) experimental setup. The thesis mainly includes:(1) Photoionizaiton of 1D semi-classical full-dynamic H2+ model: we established a 1D semi-classical fully-dynamic H2+ model by treating the protons as classical particles and the electron a quantum one. The ionization process is analyzed by numerically solving the time-dependent Schr?dinger Equation (TDSE). A method for instantaneously calculating absolute and normalized photoionization rate is proposed, based on which the charge resonance enhanced ionization (CREI) effect is observed and studied with theoretical explanations.(2) Ground state of linear Hen (n=2,3,5,7) clusters: Fundamental theories of quantum chemistry, ab initio principle, and density-functional theory (DFT) is introduced. Based on these theories, we optimized the structures of Hen clusters using appropriate sets of basis. We also calculated the molecular orbits (MO) and charge density distribution of ground states of all involved clusters, each with a series of different internuclear distances, employing the self-consistence field theory. We then constructed the numerical solution of the ground state wavefunctions by processing the obtained data according to the principles of quantum chemistry.(3) Photoionization of Hen clusters in intense laser field: the molecular orbits wavefunctions of the clusters was firstly simplified to one dimension and the grid range for numerical simulation was extended. Using the simplified 1D MO wavefunctions as initial states, we numerically solved the time-dependent Kohn-Sham Equation with optical fields added, obtaining the following results: a) for the optimized structure, the ionization shows an exponentially decayed feature, and the ionization rate is dependent on light intensity; b) Enhanced ionization effect is theoretically existing, and the peak position of enhanced ionization is smaller than the internuclear distance of the optimized structure, compared with CREI effect of H2+; c) Similarities and discrepancies of the shapes of ionization curves at different internuclear distance R is compared and analyzed; d)the relationship between the position of atoms in the cluster chain and the ionization rate is studied, with the influence of neighboring atom's potential as an theoretical explanation.(4) We described our initial idea of a TOF-MS design for experimental study of light-matter interaction. Expectations on future research work are also proposed.