Theoretical Study On The Ionization Process Of Relativistic Ion-atom And Ion-dimer Collisions

With the advent of relativistic heavy ion accelerator,the use of high-energy relativistic ions for ion-atom collision experiments has become a new way to explore the unknown physical phenomena.Unlike the non-relativistic situation,the field generated by relativistic ions no longer has spherical symmetry,which results in the particularity of the dynamics of the collision between relativistic ions and the atom system,and it has aroused great interest among atomic physicists.In addition,the field generated by relativistic ions also has extreme characteristics such as high energy density and short interaction time with atoms.Therefore,when the atomic system is subjected to such a strange interaction,it is very likely to produce unexpected physical phenomena.In this paper,we consider two relativistic collision problems from a theoretical point of view.I)Laser-assisted binary-encounter emission in relativistic ion-atom collisions.II)Double ionization of helium dimer in relativistic collisions.Starting from the basic perturbation theory,we adopted a few reasonable approximations to establish the calculation method of scattering amplitude for these two collision systems,and obtained the corresponding physical results.In our study of the Laser-assisted binary-encounter emission in relativistic ionatom collisions,we first obtained the position and width of the binary encounter peak in the relativistic collision energy region.When the laser is involved,we find that even a weak laser field that has no effect on the atom itself can significantly change the dynamics of the collision,thus having an extremely considerable impact on the electron energy spectrum.As the collision energy increases,we find that the rapid broadening of the binary encounter peak caused by the relativistic dynamics will attenuate the effect of the laser field.In the research on the double ionization of ions and helium dimers,we focused on the main reaction channel: the ionization of two helium atoms caused by the action of incident ions.Based on the Born approximation and the symmetry eikonal approximation,we have developed the theoretical models for the collision of relativistic ions with helium dimers.Our theoretical calculation results clarify the relationship between the total cross section of the double ionization channel and the spatial orientation and the internuclear distance of the helium dimer.When studying the collision between incident ions and a helium dimer with a very far nuclear distance,a very obvious relativistic effect is found when the helium dimer is perpendicular to the incident beam.In this situation,the field generated by the relativistic incident ion significantly enhances the total cross section.