A Study Of The Wave Packet Dynamics Of Diatomic Molecular With Femtosecond Pump-probe Photoelectron Spectroscopy

With femtosecond laser techniques it is now possible to observe and control the process of molecular reaction dynamics in real time and understand the mechanism of molecular reaction dynamics thoroughly. Much effort has been devoted to the development of accurate quantum dynamics methods of chemical reaction for a long time. At present, time-dependent quantum wave packet approach has emerged as a powerful theoretial tool for studying molecular reaction dynamics. The time-dependent quantum wave packet approach has been extensively applied to the field of molecular reaction dynamics.Femtosecond pump-probe photoionization is an effective technique for investigating the molecular reaction dynamics. The photoionization provides ions and photoelectrons. The ion signal detection provides time-resolved mass and kinetic-energy resolution spectra. And the photoelectron spectra can provide complementary information on the evolution of the wave packet. Therefore, the femtosecond pump-probe photoelectron spectrum technique may be employed to study processes of molecular reaction dynamics driven by ultrashort pulse laser.In the past twenty years the most processes of dissociation and ionization of NaK molecule were studied by using the weak laser fields. The lower electronic excited and ground states of NaK molecule, excluding the 61∑+ state, were widely studied in the spectroscopy of NaK molecule. The 6' ∑+ state was recently discovered. It has a double-minimum structure. Nitric oxide has abundant Rydberg and valence electronic states and is one of the most studied diatomic molecules.In this thesis, the method of time-dependent quantum wave packet dynamics is used tocalculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the 61∑+ double-minimum state of NaK and the transfers of population and charge between the Rydberg state C2II and the valence state B2II of NO in intense laser field. The calculation results indicate that the wave packet distribution of the 61∑+ state and the wave packet transfer between two states can be controlled by altering the parameters of the laser pulses. And it is possible to monitor the splitting of the wave packet at the potential barrier. In addition, we can obtain the wave packet dynamic information of the 6~1∑+ state from thephotoelectron energy spectra. For NO molecule, the valence state B2 has a considerable effect on the PES of NO molecule. Under the action of the non-adiabatic coupling, a part of populations of the Rydberg state can pour into and be trapped in the valence state. The electron transfer from the Rydberg state to valence state occurs in the crossing region of C2 and B2 potential energy curves. The time-resolved photoelectron spectra are related to the C -B coupling and the delay time between the pump and probe pulses. The C2-B2 coupling makes the photoelectron spectra of NO more complex.Theoretical model and calculations in this thesis may be important for controlling chemical reaction. The time-dependent quantum wave packet is an effective method used for studying the excitation and ionization dynamics of molecules in the femtosecond pulse laser field.