Nonsequential Double Ionization In Two-color Circularly Polarized Laser Fields

With the development of laser technology,a series of new strong field physics phenomena have been discovered.The nonsequential double ionization process of atoms or molecules under strong field action is a widely concerned topic.This process not only reflects the interaction between the laser field and electrons,but also reveals the correlation between electrons.In order to clarify the kinetic process of nonsequential double ionization in strong field,we studied the effects of laser field wavelength,electric field amplitude ratio on the nonsequential double ionization.Under the counter-rotating two-color circularly polarized laser fields,we control the atomic nonsequential double ionization process by adjusting the laser field wavelength and electric field amplitude ratio.In the theoretical calculations,the classical ensemble approach,semiclassical theory approach and direct solving quantum equation approach are used to study the nonsequential double ionization.These methods can simulate the experimental results very well.Among them,the classical ensemble approach is widely used because of its high efficiency and low computational complexity.The nonsequential double ionization of Ar atom in counter-rotating two-color circularly polarized laser fields are studied using the classical ensemble approach in this article.The results show that if the wavelength of the laser field is changed,the probability of nonsequential double ionization will be several orders of magnitude different.The electron momentum correlation spectra also reflect that the final momentum of the two electrons is related to the wavelength of the laser field.These phenomena indicate that the selection of the wavelength of the laser field has a significant effect on the process of nonsequential double ionization.The result indicates that there is a broader steerable range of the electric field amplitude ratio of the laser field to obtain higher ionization enhancement for?₂?28?3?₁than that for?₂?28?2?₁.Through the analysis of trajectories,the recollision picture for?₂?28?3?₁is complicated leading to slow change of double ionization,which is benefit to gentle control mechanism.However,the recollision ionization channel is easily distinguishable and sensitive to control double ionization in?₂?28?2?₁laser fields and the travel time can be controlled in the order of magnitude of 100 attoseconds.