A Study Of The Wave Packet Dynamics Of Li₂ Molecule With Femtosecond-Resolved Photoelectron Spectrum

With the development of the ultra-strong and ultra-fast laser pulses techniques, more and more theoretical and experimental research works have been done to study the atomic and molecular dynamics. The motion of the atomic nucleus on the potential energy surface is studied by the photoelectron spectrum theory. It has its advantages: making the space resolution possibly small, less than 1 ? and the time resolution is as small as femtosecond dimension. Presently, the methods and models which have been proposed are based on solving the Schr?dinger equation. So the theorists and experimenters are required to do many numerical calculations to solve the Schr?dinger equation, especially, quantum numerical simulations on the potential energy surface.The main work in this thesis is to calculate the time-resolved photoelectron spectra (TRPES) of the Li2 molecule by using time-dependent wave packet method. The phenomena of TRPES corresponding to different parameters are analyzed and interpreted reasonably to further study the dynamics of wave packet on E 1∑g+. To calculate the TRPES of Li2 molecule, the three-state (the first excited state of Li2 molecule, the intermediate state of Li2 molecule and the ionic state of Li2 molecule) quantum mechanical calculations are preformed. The Born-Oppenheimer approximation and the"split-operator Fourier"method are employed to solve the Schr?dinger equation in this calculation. The peaks of TRPES decreases monotonically as increasing of the pump-probe delay time (1000fs,1200fs,1400fs,1800fs,2000fs). They indicate that the wave packet has the propagation process on the shelf state area of E 1∑g+and the oscillating of the wave packet on the curve is a decreasing process. The result indicates that oscillating of the wave packet onto E 1∑g+ curve is a decreasing process of energy and the pump-probe delay time plays a prominent role in the process. At short delay time(100fs,200fs), the particular phenomenon of TRPES with four peaks is qualitatively interpreted in a dressed state picture by analyzing wave packet motion on light-induced potential (LIP). The calculation results indicate that the particular phenomenon with four peaks at short delay time is due to the appearance of light-induced potentials, and the LIP has effect on the shape of TRPES. The dramatic difference in the electronic structure of E 1∑g+ at the inner and outer turning points, also has an impact on the TRPES. The control for the first excited state A 1∑u+ of the initial wave packet is discussed.