Gießen 2007 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 12: Kernphysik / Spektroskopie

HK 12.6: Talk

Tuesday, March 13, 2007, 15:30–15:45, D

First measurement of the spin/parity and magnetic moment neutron-rich ³³Mg using β-NMR — D. Yordanov¹, •M. Kowalska², K. Blaum^2,3, K. Flanagan¹, P. Lievens⁴, R. Neugart², and G. Neyens¹ — ¹Instituut voor Kern- en Stralingsfysica, K.U. Leuven, Belgium — ²Institut für Physik, Universität Mainz, Germany — ³GSI, Darmstadt, Germany — ⁴Laboratorium voor Vaste-Stoffysica en Magnetisme, K.U. Leuven, Belgium

The well-established shell model fails in some more exotic parts of the nuclear landscape where the shell gaps and magic numbers seem different than closer to stability. One of such regions is the “island of inversion” located around Z = 10-12 and the N = 20 magic number, characterised by ground-state deformations which are surprisingly large for closed-shell nuclei. With our β-NMR spectroscopy setup, located at ISOLDE/CERN, in 2006 we continued our recent studies of the “island of inversion”. By optically pumping ³³Mg⁺ ions with UV laser light and by using the hyperfine interaction of the nucleus with atomic electrons or external magnetic fields, we have determined the hyperfine structure and the Larmor frequency of the ³³Mg nucleus. This allowed to measure for the first time the ground-state spin and magnetic moment of ³³Mg. The latter was found to have a negative sign, consistent with a large 2p2h component of the ground state wave function and corresponding to a negative parity. In the talk we will present the physics motivation of our studies, the experimental technique, as well as the results and their interpretation in the context of the shell model. (Supported by BMBF, FWO and EU)