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HK: Hadronen und Kerne

HK 50: Spectroscopy: 130 ≤ A ≤ 180

HK 50.4: Gruppenbericht

Mittwoch, 18. März 1998, 15:00–15:30, D

Search for the Decay-out of the Yrast Superdeformed Band in ¹⁴⁴Gd — •R.M. Lieder¹, S. Lunardi², D. Bazzacco², G. Falconi², R. Menegazzo², P. Pavan², C.M. Petrache², C. Rossi-Alvarez², C.A. Ur², R. Venturelli², M. DePoli³, A. Gadea³, G. de Angelis³, D.R. Napoli³, Z. Podolyak³, W. Gast¹, A. Georgiev¹, H.M. Jäger¹, H.J. Jensen¹, T. Rzaca-Urban⁴, W. Urban⁴, Z. Pytel⁴, M. Augsburg⁴, K. Starosta⁴, C.A. Kalfas⁵, C.T. Papadopoulos⁶, and R. Vlastou⁶ — ¹Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich — ²INFN, Sezione di Padova, I-35131 Padova — ³INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro — ⁴Institute of Experimental Physics, University of Warsaw, PL-00-681 Warsaw — ⁵Institute of Nuclear Physics, NCRS Demokritos, GR-15310 Athens — ⁶National Technical University of Athens, GR-5773 Athens

In order to identify discrete transitions linking the yrast superdeformed (SD) band of ¹⁴⁴Gd to the normal-deformed (ND) states an experiment has been carried out with the γ-detector array EUROBALL III at the XTU tandem accelerator of the Laboratori Nazionali di Legnaro, Italy. The final nucleus was produced with the ¹⁰⁰Mo(⁴⁸Ti,4n) reaction at 215 MeV. Information about the deexcitation of SD bands exists only for a few cases, because the intensities of the already weak SD bands fragment into so many branches that an identification of the discrete linking transitions is experimentally very difficult. This knowledge is required, however, to determine the excitation energies, spins and parities of SD bands. In the mass A=150 region a candidate for a single-step linking transition has been found only for ¹⁴³Eu [1], which has an energy of 3361 keV. The nucleus ¹⁴⁴Gd seems to be a good case to search for discrete linking transitions because the decay-out of the yrast SD band takes place below the backbending, caused by the alignment of two N=6 protons, where no high-N intruder orbitals are occupied any longer. Accordingly, the deformation is expected to be smaller than for the upper part of this SD band and a larger mixing with ND states may be expected. In the EUROBALL III experiment about 3 · 10⁹ events with an average γ-ray multiplicity of four have been collected. The analysis is in progress and the linking transition of 3361 keV in ¹⁴³Eu, which is produced as byproduct, has been confirmed. (Supported by the EU, Volkswagen Foundation and KBN).

[1] A. Ataç et al., Z. Phys. A355, 343 (1996)