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HK: Fachverband Physik der Hadronen und Kerne
HK 12: Kernphysik / Spektroskopie
HK 12.5: Talk
Tuesday, March 13, 2007, 15:15–15:30, D
Search for E0 Transitions in Mg Isotopes around the Island of Inversion* — •W. Schwerdtfeger1,3, V. Bildstein2,3, D. Habs1,3, T. Kröll2,3, R. Krücken2,3, T. Morgan1,3, O. Schaile1,3, M. Sewtz1,3, P. Thirolf1,3, and K. Wimmer1,3 for the IS414 collaboration — 1Department für Physik, LMU München — 2E12, TU München — 3Maier-Leibnitz-Laboratorium, Garching
Around the island of inversion a coexistence of spherical and deformed 0+
states in neutron rich Mg nuclei is predicted. Resulting from a fast timing
experiment on 30Mg at ISOLDE the 1789 keV state is expected to be a
candidate for the deformed 0+ state with a potentially strong E0 decay branch
to the spherical 0+ ground state. Two different estimates for ρ2(E0) can be derived (i) from the measured deformation of the 01+ state in 32Mg taken as an estimate for the deformation of the 02+ state in 30Mg and (ii) from the A−2/3 scaling based on the known value in 24Mg, resulting in ρ2(E0) ∼ 0.02 − 0.26.
In a first experiment using a Mini-Orange
spectrometer a limit for the E0 strength ρ2(E0) ≤ 0.26 (absolute intensity ≤
0.1%) could be derived. An improved experiment was done measuring E0 decay in
coincidence with β-decay. An improvement by a factor of 12 for the peak-to-background ratio was reached allowing for a reduced limit of ρ2(E0) ≤ 0.08 (absolute intensity ≤ 0.03%). However the electron spectrum still contains a sizable amount of background electrons. GEANT4 simulations have been performed in order to design a new target chamber, reducing background from Compton scattering and pair creation.
*Supported by BMBF under contract 06 ML 234.