Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 23: Nuclear Structure/Spectroscopy IV

HK 23.1: Gruppenbericht

Mittwoch, 10. März 2004, 10:45–11:15, A

Feasibility of g Factor Experiments for Radioactive Beams based on a first Measurement of Coulomb excited ⁷⁶Kr(2₁⁺) — •K.-H. Speidel¹, G. Kumbartzki², N. Benczer-Koller², K. Hiles², T.J. Mertzimekis³, M.J. Taylor⁴, M.A. McMahon⁵, L. Phair⁵, J. Powell⁵, L. Bernstein⁶, and J.R. Cooper⁶ — ¹Helmholtz-Institut für Strahlen- und Kernphysik, Univ. Bonn — ²Department of Physics and Astronomy, Rutgers. Univ. — ³Michigan State Univ. — ⁴Univ. of Brighton — ⁵LBNL Berkeley — ⁶Lawrence Livermore National Lab.

We report on a very first g factor measurement of the 2₁⁺ state of radioactive ⁷⁶Kr(T_1/2=14.8 h) demonstrating that the technique of projectile Coulomb excitation in inverse kinematics combined with transient magnetic fields allows to determine g factors of radioactive beams in general. The isotope was produced by the LBNL 88-Inch Cyclotron in the ⁷⁴Se(α,2n)⁷⁶Kr reaction and transferred to the AECR ion source of the cyclotron for acceleration to 230 MeV with intensities of ≈ 10⁸ ions/s. De-excitation γ rays from Coulomb excitation with ²⁶Mg of a multi-layered target, including a Gd layer for spin precessions, were detected in coincidence with Mg ions by four Ge Clover detectors. A turning magnetic tape placed in front of a Si solar cell was used to transport the stopped beam radioactivity to a well-shielded area. Data were taken for two hours after each production run including three cycles altogether. In addition, stable ⁷⁸Kr has been measured to determine the angular correlation and calibrate the effective transient field. The g factor deduced is discussed in the framework of the IBA-II model.