Berlin 2001 – scientific programme

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A: Atomphysik

A 2: Ion Scattering I

A 2.10: Talk

Monday, April 2, 2001, 18:00–18:15, H1028

Double-K-Vacancy Production in Li-Like Be⁺ and C³⁺ Ions Colliding With Helium. — •A. S. Al-Naser, A. L. Landers, J. A. Tanis, and S. M. Ferguson — Western Michigan University, Kalamazoo, Michigan, 49008

The formation of doubly vacant K-shell states in Be⁺ and C³⁺ ions colliding with helium has been investigated using high-resolution projectile Auger spectroscopy. In general, there is expected to be a competition between the electron-electron (e-e) and the electron-nucleus (e-n) interactions in the production of these so-called No-dqhollowNo-dq states, which depends on the strength of the perturbation parameter Z/v. In addition, variation of the parent ion species is seen to influence the relative strength of the e-e interaction.

Be⁺ and C³⁺ ions were accelerated using the tandem Van de Graaff accelerator facility at Western Michigan University. Collision energies corresponding to perturbation strengths Z/v (Z = 2) of 0.4-0.6 for He + Be⁺ and 0.22-0.45 for He + C³⁺, respectively, were investigated. For Be⁺, the doubly-vacant K-shell states are predominantly composed of two-electron 2lnl’ configurations, while for C³⁺ both two- and three-electron configurations, 2l2l’ and 2l2l’2lNo-dq, respectively, contribute. Thus, K-shell ionization plus K-shell excitation dominates the production of hollow states in Be⁺, whereas in C³⁺ double-K-shell excitation is also important. Furthermore, for Be⁺ the 2l3l’ configurations contribute significantly, while these configurations are negligible in C³⁺.