Theoretical Investigation On The Dynamic Interference Of The Atomic And Molecular Photoionization By Super-intense EUV Laser Pulses

In recent years,the development of laser technology has helped people provide a lot of help in the study of the interaction of strong fields with atoms and molecules.Under high-frequency laser pulses,atomic ionization will have some counter-intuitive changes with the increase of the laser pulse peak intensity.When the laser pulse peak intensity exceeds a critical value,as the pulse peak further strengthens,the ionization rate of the atom will not only increase near the laser pulse peak,but will be counter-intuitively stable;the photoelectron spectrum will be split from a unimodal structure to a multimodal structure,which called dynamic interference.In this paper,we use solving the Time-dependent Schr?dinger Equation?TDSE?to study the hydrogen atoms under the high-frequency laser pulses and the high-frequency chirped pulses,as well as the ionization process of hydrogen molecular ions,explore its dynamic interference phenomenon.The main contents include the following aspects:?1?Aiming at the controversy over the existence of dynamic interference of hydrogen atoms in the ground state,we investigated the ionization process of super-intensity lasers and hydrogen atoms.The results confirmed the dynamic interference phenomenon of the ground-state hydrogen atom,and the change of the electron ionization rate with time under high-intensity laser pulse was studied.This thesis further describes the effects of atomic stability and AC Stark shift on the ionization process of atoms under the high-frequency laser pulses.It is found that when the peak value of the pulse increases to a certain value,with the arrival of the peak value of the laser pulse,the ionization rate will stabilize,the atom will no longer ionize,and the ionization will continue to occur at the falling edge of the pulse The photoelectron spectrum will appear as a multimodal structure with increasing pulse peak intensity.?2?Aiming at the occurrence of chirp due to dispersion and non-linear effects during the generation of laser pulses,we further explored the photoionization of hydrogen atoms from the ground state at chirped pulses.We have studied the photoelectron spectroscopy of hydrogen atoms using chirp laser pulses,and the results show that with the increase of linear chirp,the dynamic interference effect of the pulses will weaken and the red shift phenomenon will be found.Our results can explain the weakening of interference by the principle of dynamic interference;at the same time,the effect of chirped pulses on the dynamic interference is compared with the time when there is no chirp.The difference between dynamic interference with chirp and without chirp is compared by intuitive comparison of instantaneous ionization rate.?3?The chirped pulses for two different expressions,which are commonly used in experiments and theory are compared.We compare the dynamic interference phenomenon of ground state hydrogen atoms under these two kinds of chirped pulses.In this paper,we compare two forms of linear chirp Gaussian ultrashort pulses?e.g.,fwhm and equal power laser pulses?and find that the expressions of both forms can significantly change the photoelectron spectrum,such as weakening the interference pattern,but they There are many different characteristics.By discussing the instantaneous photoionization rate and considering the stabilization effect of atoms and the AC Stark shift,it is revealed how different forms change the dynamic interference pattern.?4?We further explored the more complex the ionization process of H₂⁺,we found the same as the hydrogen,H₂⁺can also be observed that the dynamic interference phenomenon and then we compare the sensitivity of photoelectron momentum distribution in the different laser parameters?laser intensity,the center frequency and pulse duration?,and different internuclear distance,orientation of H₂⁺,and to explore the difference between their influence on the dynamic interference.