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6th International Symposium on Swift Heavy Ions Matter - SHIM 2005, Aschassenburg : Allemagne (2005)
Electron gas polarization effect induced by heavy H-like ions of moderate velocities channeled in a silicon crystal
E. Testa1, D. Dauvergne1, A. Bräuning-Demian2, F. Bosch2, H. Bräuning3, M. Chevallier1, C. Cohen4, A. Gumberidze2, S. Hagmann2, A. L'Hoir4, R. Kirsch1, C. Kozhuharov2, D. Liesen2, P.H. Mokler2, J.-C. Poizat1, C. Ray1, J.-P. Rozet4, Th. Stöhlker2, S. Toleikis2, M. Toulemonde5, P. Verma2

We report on the observation of a strong perturbation of the electron gas induced by 20 MeV/u U91+ ions and 13 MeV/u Pb81+ ions channeled in silicon crystals. This collective response (wake effect) induces a shift of the continuum energy level by more than 100 eV, which is observed by means of radiative electron capture into the K- and L-shells of the projectiles. We also observe an increase of the REC probability by 20–50% relative to the probability in a non-perturbed electron gas. The energy shift is in agreement with calculations using the linear response theory, whereas the local electron density enhancement is much smaller than predicted by the same model. This shows that, for the small values of the adiabaticity parameter achieved in our experiments, the density fluctuations are not strongly localized in the vicinity of the heavy ions.
1 :  IPNL - Institut de Physique Nucléaire de Lyon
2 :  GSI - Gesellschaft für Schwerionen Forschung
3 :  Institut für Kernphysik
4 :  INSP - Institut des Nanosciences de Paris
5 :  CIRIL (GANIL) - Centre Interdisciplinaire de Recherche Ions Lasers
Physique/Physique/Physique Atomique
Channeling – Highly charged ions – Radiative electron capture (REC) – Wake effect