Berlin 2001 – wissenschaftliches Programm
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A: Atomphysik
A 12: Posters Thursday (Ion/Atom/Molecule/Surface Scattering)
A 12.21: Poster
Donnerstag, 5. April 2001, 12:30–15:00, AT3
Unexpected X-ray Emission Due to Formation of Bound Doubly-Excited States — •Reinhold Schuch1, Stojan Madzunkov1, Eva Lindroth1, and Dan Fry2 — 1Department of Atomic Physics, Stockholm University, S-10405 Stockholm, Sweden — 2Department of Physics, Kansas State University, Manhattan, KS 66506, USA
We report here on evidence of a strong di-electronic effect when slow highly charged ions (HCI) capture single electrons from atoms in the gas phase. The x-ray spectra which are, to our knowledge, observed for the first time for single capture exclusively with slow HCI, show interesting cascading features for both an initially filled and unfilled M shell. From comparison with cascading calculations for the initially open M shell case we can derive the angular momentum of the state the electron is captured into.
A key point is that even when the HCI (Taq+, q=39-48) has an initially filled M shell, one observes intense M x-ray emission in coincidence with singly charged target-recoils. This is explained by the formation of bound doubly-excited states through electron correlation. An elaborate theoretical treatment shows that bound doubly excited states are mixed with states where a Rydberg electron is bound in the core of a highly charged ion. It is striking that this occurs with a large probability (close to unity), and one needs to assume that higher Rydberg states are populated than predicted by the over-barrier model in order to explain the experimental results. The Rydberg electron seems to be able to excite the strongly bound core of the highly charged ion in a correlated two-electron process. The M x-ray is emitted when this core excited state decays.