Düsseldorf 2007 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 11: Poster I - Collisions with electrons and ions
A 11.1: Poster
Dienstag, 20. März 2007, 16:30–18:30, Poster B
Projectile excitation in relativistic ion–atom collisions: Alignment of excited ionic states — •Stephan Fritzsche1, Thomas Stöhlker2, Andrey Surzhykov3, and Ulrich D. Jentschura3 — 1Universität Kassel — 2Gesellschaft für Schwerionenforschung (GSI), Darmstadt — 3Max–Planck–Institut für Kernphysik, Heidelberg
Both, the electron capture and Coulomb excitation of heavy projectile ions at storage rings lead to an alignment of the resulting excited ionic states with respect to the beam direction. Such an alignment results subsequently in the emission of characteristic x–ray photons which have an anisotropic angular distribution as well as a nonzero linear polarization. While the (angular and polarization) properties of the characteristic radiation following capture processes have been studied in great detail during the last two decades, less attention has been paid to the Coulomb excitation of the projectiles by the (screened) charge of the target atoms. Only recently the “excitation–and–decay” process have been observed at the GSI facility in Darmstadt for the helium–like uranium U90+ ions. The measured alignment of the 1s 2p3/2 J = 1 excited state was found, however, to be inconsistent with the predictions of a simple one–particle model. In this contribution, therefore, we present a theoretical study of the Coulomb excitation process, based on the Dirac’s relativistic equation and the semi–classical approximation, which takes into account the multi–electron aspect of the helium–like ions. By using our theoretical approach, predictions are given for the alignment of the 1s 2p3/2 J = 1, 2 states of high–Z projectile ions and are compared with available experimental data.