Contributions of multi-electron processes to inner-shell charge transfer and vacancy production: projectile charge dependence in collisions of bare nuclei with argon

Previous coupled-channels calculations of inner-shell charge transfer and vacancy production for p+Ar collisions are extended to bare projectiles with nuclear charges Z p =2 and 6, in the collision energy range from 1 to 9 MeV amu -1 . An improved expression for the charge transfer amplitude is derived in a 'distorted-phase' formulation of the impact parameter method. The authors denote by sigma C,VK the inclusive cross section, which has been measured by coincidence experiments, for producing all final states in which at least one target electron has been transferred to the projectile and at least one vacancy has been produced in the target K shell. In the single-particle model sigma C,VK reduces to sigma SP C,VK , which contains only the exclusive single-electron process of direct transfer from the target K shell. The contributions of multi-electron processes to their calculated sigma IPM C,VK increase strongly with Z p . For Z p =6, sigma IPM C,VK differs by up to a factor of three from sigma SP C,VK . The charge transfer cross sections sigma IPM CT and sigma IPM C,VK show a Z p dependence less than the Z 5 p of the OBK approximation. The calculated sigma IPM VK and sigma SP I,VK for Z p =6 are compared with experimental K vacancy production cross sections for C 6+ and C 4+ projectiles, respectively, and good agreement is found.