Atomic Ionization By Super-intense And Ultrashort Extreme Ultraviolet Laser Pulses

The development of laser technology has made laser an important tool detecting the dynamic process of atomic and molecular.Due to the characteristics of high-intensity of lasers,many higher-order nonlinear physical phenomena such as above-threshold ionization?ATI?,non-sequential double ionization?NSDI?,and higher harmonic generation?HHG?have been discovered and studied deeply.In recent years,with the establishment of free electronic laser devices in various countries around the world,the generation of super-high intensity extreme ultraviolet laser light sources has become possible.Atomic above-threshold ionization under such super high intensity laser pulses has been found some new physical phenomena.For example,dynamic interference is one of which,related researchs show that with super high-intensity laser pulses,atomic ionization will not happen,that names atomic stabilization.Such atomic stabilization can cause a double-slit structure in the time domain during the process of photoionization by super intense laser pulses,and the photoelectron wave packets from the structrure interferece finally.Our work mainly discusseed the hydrogenic atomic photoelectron momentum distribution?PMD?under different laser conditions by adjusting the laser parameters,and studied the ionization process of ground state hydrogen atoms.The research content mainly includes the following two terms.1.We theoretically studied the PMD of ground-state hydrogen atoms exposed to the extreme polarization pulsed lasers with different polarizations.By comparing the PMD of ground-state hydrogen atoms with linear polarized laser and circular?elliptical? polarized laser,it is found that when the laser intensity is low(I₀<1×10¹⁸W/cm²)the dynamic interference fringes of PMDs with different polarized lasers have no significant difference,and PMD under the circular polarized laser can be obtained by superimposing the results of mutually perpendicular linearly polarized laser simply.For higher intensity laser(I₀?5×10¹⁸W/cm²),the Coulomb effect becomes obvious.The photoelectrons are driven by the linearly polarized laser collide with the nucleus and are scattered at certain angle.Therefore,the PMD of ground-state hydrogen atoms under the circular polarized laser no longer satisfies the law above-mentioned.2.We theoretical studied the PMD of ground-state hydrogen atoms exposed to a few-cycles extreme ultraviolet laser pulse.By changing the laser intensity and pulse envelope phase we have controled the asymmetry of the hydrogen atomic PMD.?1?By changing the phase of the pulse envelope,we found that when CEP=0,the photoelectron momentum is symmetrically distributed in the laser polarization direction;when CEP=?/2,the asymmetry of the PMD is most clear.?2?By changing the laser intensity,we got the phenomenon similar to the CEP effect,and we found that as the peak intensity of the laser increases,the ionization moment moves forward,and the momentum distribution of the photoelectrons become asymmetry.