Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 36: Nuclear Structure and Dynamics I

HK 36.4: Talk

Tuesday, March 17, 2009, 17:15–17:30, H-ZO 40

Isomeric ratios for nuclei with Z=62-67 and A=142-152 produced in the relativistic fragmentation of 208Pb — •Szymon Myalski¹, Adam Maj¹, and Zsolt Podolyak² — ¹IFJ PAN, Kraków,Poland — ²Dept. of Physics, Univ. of Surrey, Guildford, UK

We have investigated isomeric states in a number of nuclei with Z=62-67 and A=142-152, produced by the fragmentation of the relativistic(1 GeV/u)²⁰⁸Pb beam from the SIS-18 synchrotron of the GSI facility on a ⁹Be target, and selected by the FRagment Separator(FRS). The selected nuclei of interest were implanted into the stopper, a block of plastic 7mm thick. The gamma-rays from the decay of isomeric states in the implanted nuclei were measured by the high purity germanium array, RISING. In total 22 nuclides were detected, isomeric states were observed in 9 of them:19⁻in ¹⁵²Ho, 31/2⁺in ¹⁵³Ho, 27⁺in ¹⁴⁸Tb, 10⁺in ¹⁴⁴Gd, 49/2⁺in ¹⁴⁷Gd, 11/2⁻in ¹⁴³Eu, 8⁻in ¹⁴⁴Eu, 11/2⁻ in ¹⁴⁵Eu, 10⁺in ¹⁴²Sm and 7⁻in ¹⁴²Sm. Of special interest is the 27⁺ state in ¹⁴⁸Tb, the highest spin populated through the fragmentation reaction until present day. The aim of this work was the extraction of isomeric ratios(R) for these isomeric states. The R is the number of ions populated in a given isomeric state compared to the total number of ions populated for the selected nuclide. The R can provide information about the production reaction and nuclear structure. It was evaluated based on flight time, half-life, in-flight losses and by considering the finite measurement time. Results were compared with theoretical predictions, calculated using an abrasion-ablation approach.