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A: Atomphysik
A 10: Poster I: Wechselwirkung mit Elektronen und Ionen
A 10.5: Poster
Tuesday, March 14, 2006, 16:30–18:30, Labsaal
Charge Exchange of Highly Charged Ions from the Berlin EBIT with a Gas Target — •Frances Allen, Christoph Biedermann, Rainer Radtke, and Gerd Fussmann — Institut für Physik der Humboldt-Universität zu Berlin, AG Plasmaphysik, Newtonstraße 15, 12489 Berlin and Max-Planck-Institut für Plasmaphysik, Bereich Plasmadiagnostik, EURATOM Association, Germany
Highly Charged Ions (HCIs) are produced nearly at rest with an Electron Beam Ion Trap (EBIT) and extracted with a potential of 5 kV for interactions with a gas target. The ions in the extraction pulses are selected according to their mass-to-charge ratio using a Wien filter and the target gas is injected into the beamline using a pulsed supersonic jet.
When a HCI approaches a gas neutral, electron capture into Rydberg states of the ion occurs. The classical over-the-barrier (COB) model for slow HCIs describes this process and predicts the principle quantum number (n) of the state into which the electron is transferred. The excited electron then cascades to ground level resulting in a radiative emission spectrum characteristic of the interacting species and the capture state.
For charge exchange between Arq+ (q=17,18) ions and Ar neutrals the COB model predicts preferential capture into n=8. Theoretical emission spectra for electron capture into all the n=8 orbital angular momentum (ℓ) states of Ar17+,18+ have been calculated and are compared with experimental spectra measured with an x-ray detector. Of particular interest is the velocity dependence of the ℓ-capture state and deceleration grids before the target enable investigation with ions of energies below 100q eV.