Nonsequential Double Ionization Of Mg Atoms Driven By Strong Laser Fields

In recent years,with the development of ultrafast intense laser technology,the ionization process of atoms and molecules driven by strong laser fields has always been one of the most attractive research direction of strong field physics.For rare atoms,such as He,Ar,Xe,the process of nonsequential double ionization,both theoretically and experimentally,have been thoroughly studied.These studies show that in linearly polarized laser fields the mechanism of nonsequential double ionization is the recollision,but in elliptically or circularly polarized laser fields,the recollision is suppressed,the nonsequential double ionization can not occur.But for Mg atoms,experimental research show that under the driven of circularly polarized laser fields,nonsequential double ionization happen and the mechanism is still the recollision.But at present the understanding for the dynamics,and electrons correlated behavior of nonsequential double ionization of Mg atoms,especially for nonsequential double ionization driven by mid-infrared laser pulses are unclear.This thesis mainly investigates the correlated electron dynamics for the nonsequential double ionization of Mg driven by strong-field,and the corresponding dependency on the laser wavelength and the laser polarization.The full work mainly includes two aspects are as following:(1)Using the three-dimensional classical ensemble model,we systematically investigate strong-fields nonsequential double ionization dynamics of Mg from near infrared to mid-infrared.The double ionization probability of Mg as a function of laser intensity under different ellipticity is calculated.The results show that in elliptically and circularly polarized laser fields,the double ionization yield decreases sharply and the knee structure finally disappears as the laser wavelength increases.We also analyze the wavelength dependence of correlated electron momentum spectrum,and find that the correlated behavior in the correlated electron momentum spectrums becomes more pronounced as the wavelength increases.In addition,we find that in circularly polarized laser fields the recollision distance of two electrons becomes smaller with the wavelength increasing.(2)Using the two-dimensional semiclassical ensemble model,we study nonsequential double ionization of Mg driven by two-color circularly polarized laser fields,and systematically analyze nonsequential double ionization dynamics of Mg under the different laser intensity ratio.When the laser intensity ratio I800/I1600is 3.16,the double ionization probability shows a maximum.As the laser intensity ratio increases,a counterclockwise rotation in the electron momentum spectrum of the laser polarized direction is seen.Based on the time delay of the nonsequential double ionization events,electrons are divided into two kinds: recollision-induced direct ionization and recollision-induced excitation with subsequent field ionization.Then we respectively analyze the angular distribution of these two kinds of electrons at the end of the laser pulses,we find that the rotation is caused by recollision-induced excitation with subsequent field ionization,which is because of the coulomb potential of electron-electron ineraction and electron-nucleus interaction.