The Theoretical Study Of Nonsequential Double Ionization Of Argon And Xenon In Intense Laser Fields

Up to now,the interaction between light and matter is the one of the hot topics of physics study.With the rapid development of the laser technology,people have explored physical phenomena under strong laser fields,and found many novel physical phenomena,such as,Multiphoton ionization(MPI)? Above-threshold ionization(ATI)?High harmonic generation(HHG)?Nonsequential double ionization(NSDI),etc.Among them,the nonsequential double ionization of atoms or molecules in strong laser fields have contained many electron correlation information,which is the one of the important tasks in strong-field physics.There are many methods to research phenomena of nonsequential double ionization,measuring double electron energy spectrum ?measuring ion momentum spectrum and by Cold target recoil ion monmentum spectrometer(COLTRIMS)technology obtains double electrons correlated momentum spectrum,etc.In order to further explore the physical mechanism of the nonsequential double ionization between two electrons and analyze deeply the problems of multi-electron correlation,we can adjust the laser parameters(laser field intensity ?laser wavelength?pulse width)to explore further.In order to explain and analyze physics mechanism of experimental observationresults,several calculation methods have been invented,which include pure quantum method,classical ensemble method and semi-classical method.The simulated theoretical results can be consistent with the experimental observation results.Among them,The classical ensemble method has the characteristics of high calculation efficiency,less resources and convenient physical phenomena analysis,which has become a frequently used calculation method.In this paper,the classical ensemble approach is used to establish a theoretical model in order to explore the double ionization physical mechanism between the double electrons,and understand the characteristics of the correlation between electron and electron.Firstly,we use the two-classical ensemble approach to study double ionization dynamics of argon atoms under few cycle linearly polarized laser fields by theoretical studies.Here,We analyze the electron correlations of Ar atom in linearly polarized laser fields with carrier-envelope-phase(CEP)in detail.We select for three typical laser intensities to analyze the ratio of ionization number between the definite mechanism(RESI and RII channels)and total ionization versus CEPs,which induced different phenomena for recollision,induced excitation with subsequent ionization(RESI)and the recollision-induced ionization(RII)channels.At higher laser intensity,as the carrier envelope phase increasing,the process of RII channel is enhanced and RESI channel is suppressed,however,at lower laser intensity,the process of RESI channel is enhanced and RII channel is suppressed.The ionized electron can obtain enough energy to make the second electron ionize directly at higher intensity as RII channel,however,the second electron is promoted to an excited state after recollision and obtains enough energy from the subsequent laser field at lower intensity as RESI channel.By discussing double electrons correlated momentum distribution and statistical distributions of recollision time for different CEPs,there is only single recollision event in nonsequential double ionization process.These results indicates that CEPs are an important key in the correlated electron momentum distribution,which shows the significant CEPs effect in non-sequential double ionization.Secondly,we use the three-classical ensemble approach to study the wavelength effects to nosequential double ionization process of xenon atoms under few cyclelinearly polarized laser fields and elliptical polarized laser fields,By selecting three kinds of wavelength,we calculate and simulate the correlated electron momentum distributions in linearly polarized laser fields and elliptical polarized laser fields,which can be found that wavelengths play an important role in RESI and RII channels.Finally,we also analyze and simlate the statistical counts of delay time,which indicates that RII channel mainly turns on in linearly polarized laser fields and RESI channel mainly turns on in elliptical polarized laser fields.