Theoretical Study Of Molecular Orientation And Ionization Dynamics In Laser Field

Studying the interaction between light and matter is an important topic of molecular reaction dynamics,and it is also a topic of interest in other disciplines such as chemistry,biology,medicine,agronomy,materials science and microelectronics.It has important applications in high-tech fields,such as quantum electronic devices,micro-nano processing technology,LED(light-emitting diode)and self-luminous materials,laser treatment technology,and precision measurement technology.The use of laser pulses to control the molecular orientation and photoionization dynamics is a very significant topic in the field of molecular reaction.This thesis uses the time-dependent quantum wave packet theory method to study the molecular pre-orientation and ionization dynamics in laser field.The main works in this thesis are as follows:(1)We propose to use a combination of femtosecond two-color pulse chain and single-cycle terahertz pulse to orient the polar diatomic molecule LiH.The femtosecond two-color pulse is to generate high molecular vibrational status.The single-cycle terahertz pulse is used to generate rotational transitions and orient the molecule.The calculation results show that the parity number of the two-color pulse chain N has different influence on the molecular orientation degree.When N=1,3 and5,the population of oriented molecules are mainly distributed in ? =1 vibrational status;when N=2,4 and 6,the population of oriented molecules are mainly distributed in ?=0 vibrational status.The calculated maximum positive and negative molecular orientations were 0.58 and-0.63,respectively.(2)We discuss the influence of orientation on the ionization process.First,we use a single-cycle terahertz pulse to orient the NaK molecule in the ground state,and then the femtosecond pump and probe pulses are used to excite and ionize the pre-oriented molecule.We discuss the influence of molecular pre-orientation on ionization probability,angle-resolved photoelectron spectrum and photoelectron angular distribution.The results show that the ionization probability,angle-resolved photoelectron spectrum and photoelectron angular distribution are closely related to the orientation duration and degree.In the orientation duration,the higher the degree,the higher the ionization probability,and the more concentrated the photoelectronsignals.Moreover,we discuss the Autler-Townes(AT)splitting phenomenon by the superposition of pump and probe pulses.