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HK: Physik der Hadronen und Kerne

HK 16: Nuclear Structure/Spectroscopy II

HK 16.4: Vortrag

Dienstag, 9. März 2004, 16:45–17:00, A

Optical polarization and β-asymmetry measurement on neutron-rich magnesium isotopes — •M. KOWALSKA¹, K. BLAUM², D. BORREMANS³, S. GHEYSEN³, P. HIMPE³, S. MALLION³, P. LIEVENS³, R. NEUGART¹, G. NEYENS³, N. VERMEULEN³, and D. YORDANOV³ — ¹University of Mainz, Germany — ²ISOLDE-CERN, Switzerland — ³K.U. Leuven, Belgium

The properties of neutron-rich Mg isotopes around N = 20 are very much influenced by intruder states from the f_7/2 shell entering into the sp shell. This “island of inversion” is a challenge for nuclear shell-model calculations, and measurements of magnetic dipole and electric quadrupole moments are important as an experimental basis. For this purpose we have recently tested the conditions of β-NMR spectroscopy on short-lived Mg isotopes. 60 keV ion beams of ²⁹Mg, ³¹Mg and ³³Mg, produced by the RILIS ion source at ISOLDE-CERN, were polarized by collinear optical pumping with frequency-doubled laser light at 280 nm and were implanted into a cubic MgO crystal. Observation of the β-decay asymmetry as a function of the Doppler-tuned optical excitation frequency reveals the hyperfine structure of ²⁹Mg and ³¹Mg in the 3s ²S_1/2 → 3p ²P_3/2 resonance transition. Preliminary information from these measurements about the involved spins and magnetic moments will be discussed. The observed asymmetries of up to 6% will allow us to perform accurate β-NMR measurements, from which g-factors and quadrupole moments can be deduced (supported by BMBF).