Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 12: Posters Thursday (Ion/Atom/Molecule/Surface Scattering)

A 12.11: Poster

Donnerstag, 5. April 2001, 12:30–15:00, AT3

Cusp-Electron Production due to Transfer Ionization in He²⁺ + He Collisions — •László Lugosi, László Sarkadi, and Ákos Kövér — Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), H-4001 Debrecen, Pf. 51, Hungary

Cusp-electron emission (i.e., continuum electrons emitted along the ion beam direction and traveling with the beam velocity) has been investigated in 25–75 keV/amu He²⁺ on He collisions. Two processes which contribute to cusp electrons for this collision system, Electron Capture to the Continuum (ECC) and Transfer Ionization (TI), were distinguished by detecting the electrons in coincidence with the charge-state analyzed outgoing He²⁺ and He⁺ projectiles, respectively. We are particularly interested in the two-electron TI process in which the continuum-electron emission is associated with capture of a second electron into one of the bound states of the projectile. The ratio of the electron yields for the TI and ECC channels provides information on the role of the electron – electron interaction (correlation). We obtained a surpisingly large value for the TI/ECC ratio at 25 keV/amu, 1.43± 0.14, which means that the probability of the two-electron process exceeds that of the one-electron process. This result is unexpected, because in a previous experiment [1] for Ar target we obtained a smaller value (0.799± 0.080) at the same impact energy.

[1] L. Víkor et al., Nucl. Instr. Meth. B 124 (1997) 342