# Dresden 2011 – wissenschaftliches Programm

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# A: Fachverband Atomphysik

## A 26: Poster III

### A 26.54: Poster

### Donnerstag, 17. März 2011, 16:00–18:30, P2

**Direct Determination of the Magnetic Quadrupole Contribution to the Lyman-****α**_{1}** Transition in a Hydrogen-like Ion** — •Günter Weber^{1,2,3}, Harald Bräuning^{1}, Andrey Surzhykov^{1,3}, Stephan Fritzsche^{1,4}, Siegbert Hagmann^{1}, Renate Märtin^{1,3}, Regina Reuschl^{1}, Uwe Spillmann^{1}, Sergiy Trotsenko^{1,2}, Danyal Winters^{1}, and Thomas Stöhlker^{1,2,3} — ^{1}GSI, Darmstadt, Germany — ^{2}Helmholtz-Institut Jena, Germany — ^{3}Physikalisches Institut, Universität Heidelberg, Germany — ^{4}Department of Physics, University of Oulu, Finland

By applying novel-type position sensitive x-ray detectors as Compton polarimeters we performed the first linear polarization measurement of the Lyman-α_{1} radiation (2p_{3/2} -> 1s_{1/2}) in a high-Z system, namely in U^{91+}. Here, we observed an interference between the electric-dipole (E1) and the magnetic-quadrupole (M2) tranistion amplitudes leading to a significant depolarization of the Lyman-α_{1} radiation. In the present work, we show that a combined measurement of the linear polarization and of the angular distribution enables a very precise determination of the ratio of the E1 and the M2 amplitudes and the corresponding transition rates without any assumptions concerning the population mechanism for the excited 2p_{3/2} state. This finding opens a new route to disentangle the population process of the excited ionic state from the subsequent decay properties. The accuracy of the obtained amplitude ratio will stimulate more detailed quantum-electrodynamical investigations on the transition amplitudes of highly-charged ions beyond Dirac’s theory.