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HK: Fachverband Physik der Hadronen und Kerne

HK 41: Kernphysik / Spektroskopie

HK 41.2: Talk

Thursday, March 15, 2007, 11:30–11:45, B

Test of the critical point symmetry X(5) in the mass region A=180 — •barbara melon¹, alfred dewald¹, oliver moeller¹, thomas pissulla¹, christoph fransen¹, jan jolie¹, andreas linnemann¹, pavel petkov², dimitar tonev³, giacomo de angelis³, dino bazzacco³, calin ur⁴, roberto menegazzo⁴, enrico farnea⁴, and karl oscar zell¹ — ¹IKP, Universität zu Köln, Köln, Germany — ²Bulg. Acad. of Sciences, Inst. for Nucl. Res. and Nucl. Ener., Sofia, Bulgaria — ³INFN, LN di Legnaro, Italy — ⁴Dip. di Fisica, Universita’ and INFN Sez. Padova, Italy

Recently, the first examples of X(5) like nuclei in the mass region A=180 have been identified, ^176,178Os. We report on further results of a lifetime measurement performed at the LN Legnaro using the Köln coincidence plunger device and the GASP spectrometer. Excited states were populated via the reaction ¹⁵²Sm(²⁹Si,5n)¹⁷⁶Os at E(²⁹Si) = 145 MeV. Special effort has been made to reduce the experimental uncertainty of the B(E2, 2₁⁺→0₁⁺) value in ¹⁷⁸Os, used for transition strength normalizations in ¹⁷⁸Os necessary for the comparison with theoretical models. A second experiment was performed to measure the lifetime of the first excited 2⁺ state in ¹⁷⁸Os with the Köln coincidence plunger device at the FN Tandem accelerator of the University of Cologne using THE ¹⁶⁶Er(¹⁶O,4n)¹⁷⁸Os reaction at E(¹⁶O) = 80 MeV. The resulting lifetime has been compared to the value obtained using the delayed coincidence method.

Supported partly by the European Union TMR Program, contract HPRI-CT-1999-00083