Universal cross sections for K-shell ionization by heavy charged particles. II. Intermediate particle velocities

George Basbas, Werner Brandt, and Roman Laubert
Phys. Rev. A 17, 1655 – Published 1 May 1978
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Abstract

Experimental K-shell ionization cross sections of Al13 and Ni28 are reported for ions of H11, H12, He24, Li36, and Li37 with kinetic energies in the range from 2 to 36 MeV, and of Ni28 for ions of C612, O816, and F919 in the range from 4 to 90 MeV. The theory of direct Coulomb K-shell ionization, as developed in an earlier paper [Phys. Rev. A 7, 983 (1973)] for projectiles of atomic number Z1, small compared to the target atomic number Z2, and of velocities v1 small compared to the target K-shell electron velocity v2K, i.e., v1v2K, is extended to intermediate velocities v1v2K. New effects appear. They add to the Z12-proportional cross sections one derives from linear-response theories for direct ionizations. They are attributed to the polarization of the target K 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 v1v2K, such contributions subside, and one retrieves the cross sections of the linear-response approximation. The theory predicts K-shell ionization cross sections for projectiles with Z1Z2<0.5 at all velocities in a comprehensive manner. It agrees with experimental data covering six orders of magnitude for collisions partners with Z1Z2 ranging from 0.03 to 0.3 and v1v2K from 0.07 to 2.

  • Received 2 May 1977

DOI:https://doi.org/10.1103/PhysRevA.17.1655

©1978 American Physical Society

Authors & Affiliations

George Basbas*, Werner Brandt, and Roman Laubert

  • Department of Physics, New York University, New York, New York 10003

  • *Present address: Dept. of Physics, North Texas State University, Denton, Texas 76203.

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Vol. 17, Iss. 5 — May 1978

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