Electron Vortex Of He~+ And He In The Combined Laser Field

The electron transition occurs after the laser pulse interacts with atoms and molecules,and then the photoelectron momentum distribution(PMD)is formed.Changing the frequency of two circularly polarized laser pulses will produce a more complex structure of electron vortices,which contain rich physical information.The appearance of the electronic vortex structure provides a new direction for the study of strong field atomic and molecular dynamics.In this paper,by solving the two-dimensional time-dependent Schr?dinger equation(2D-TDSE),the PMD and electron vortices produced by the two-photon ionization of He⁺in a combined co-rotating and counter-rotating elliptically polarized laser field with a time delay are explored.When the angular frequency relationship of the laser pulse is?₂=?₁=1.14 a.u.,the PMD and electron vortex is explained by the Attosecond Perturbation Ionization Theory.The PMD and its electron vortex of He⁺in the co-rotating laser field present an approximate ring.In the counter-rotating laser field,the PMD and electron vortex of He⁺appear spiral arms,which are distributed in four spiral arms.Then change the laser pulse wavelength to make the laser pulse angular frequency relationship?₂=2?₁=2.28 a.u.,the He⁺PMD and electron vortex in the co-rotating laser field are distributed in a spiral arm,and the He⁺PMD and electron vortex in the counter-rotating laser field.The vortex is distributed with three spiral arms.Constantly changing the ellipticity of the laser field,analysis shows that as the ellipticity of the laser field increases,the PMD distributed along the y-axis direction will expand accordingly.We have also studied the direction of rotation of the electronic vortex structure in the co-rotating and counter-rotating elliptically polarized laser fields,which is determined by the polarization direction of the relatively large wavelength laser pulse in the combined laser field.And theoretically through the generalized quantum trajectory Monte Carlo(GQTMC)method,the PMD and electron vortex of He phenomenon have been studied.With the help of semi-classical analysis,it is determined that the phase difference?S derived from the path difference between the two photoelectron wave packets caused by two continuous laser pulses affects the vortex structure,resulting in a different number of interference arms forming the vortex structure,and The vortex structure is affected by the intensity and wavelength of the laser.