Abstract
Experimental -shell ionization cross sections of and are reported for ions of , , , , and with kinetic energies in the range from 2 to 36 MeV, and of for ions of , , and in the range from 4 to 90 MeV. The theory of direct Coulomb -shell ionization, as developed in an earlier paper [Phys. Rev. A 7, 983 (1973)] for projectiles of atomic number , small compared to the target atomic number , and of velocities small compared to the target -shell electron velocity , i.e., , is extended to intermediate velocities . New effects appear. They add to the -proportional cross sections one derives from linear-response theories for direct ionizations. They are attributed to the polarization of the target shell in the field of the projectile, and to electron capture by the projectile. Guided by the perturbed stationary-state theory of atomic collisions, the polarization effects are incorporated so that the theory retains the unifying aspects of the cross sections derived in the plane-wave Born approximation, but the variables now contain the nonlinear effects as scaling factors. Electron-capture cross sections are added. When , such contributions subside, and one retrieves the cross sections of the linear-response approximation. The theory predicts -shell ionization cross sections for projectiles with at all velocities in a comprehensive manner. It agrees with experimental data covering six orders of magnitude for collisions partners with ranging from 0.03 to 0.3 and from 0.07 to 2.
- Received 2 May 1977
DOI:https://doi.org/10.1103/PhysRevA.17.1655
©1978 American Physical Society