Göttingen 1997 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 51: Kernspektroskopie, mittelschwere Kerne III
HK 51.3: Gruppenbericht
Mittwoch, 26. März 1997, 17:45–18:15, HS E
Study of superdeformed bands in 143−145Gd — •R.M. Lieder1, T. Rzaca-Urban2, W. Gast1, A. Georgiev1, H.M. Jäger1, H.J. Jensen1, E. van der Meer1, St. Utzelmann1, D. Bazzacco3, S. Lunardi3, N.H. Medina3, R. Menegazzo3, C.M. Petrache3, C. Rossi-Alvarez3, C.A. Ur3, L.H. Zhu3, G. de Angelis4, D.R. Napoli4, and R. Wyss5 — 1Institut für Kernphysik, KFA Jülich, D-52425 Jülich — 2Institute of Experimental Physics, Warsaw University, PL-00-681 Warsaw — 3INFN, Sezione di Padova, I-35131 Padova — 4INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro — 5Royal Institute of Technology, S-104 05 Stockholm
Superdeformed (SD) bands in 143−145Gd have been studied at the Tandem XTU accelerator of the LNL utilizing the γ-detector array GASP, which consists of 40 escape-suppressed Ge detectors and an inner ball of 80 BGO scintillators. The nucleus 143Gd has been studied to search for the transition from the superdeformed shapes observed for 144−150Gd to the highly deformed shapes found in 139,141Gd. The nucleus 143Gd was produced via the 97Mo(51V,p4n) reaction at a beam energy of 238 MeV.The target consisted of two self-supporting foils of 0.5 mg/cm2. The protons have been detected with the 4π charged-particle detector array ISIS, mounted inside the GASP spectrometer. A SD band has been established in 143Gd indicating that the shape transition can be expected for 142Gd. Excited SD bands have been studied in 144Gd which was produced via the 100Mo(48Ti,4n) reaction at a beam energy of 215 MeV. A stack of three targets of 0.4 mg/cm2 has been used. Four excited SD bands have been found which form two pairs of signature partners and do not show the strong band crossing observed in the previously known yrast SD band [1]. Since the crossing in the latter band results from the alignment of an i13/2 quasiproton pair it has to be concluded that this orbital is blocked in case of the excited SD bands. To measure quadrupole moments for SD bands in 144,145Gd the Doppler-shift attenuation method has been applied. The highly excited recoils were stopped in a suitable backing behind the target. For 144Gd the same reaction as above has been used and 145Gd was produced via the 114Cd(36S,5n) reaction at a beam energy of 182 MeV. For the yrast SD band in 144Gd a quadrupole moment of Q∘ 14 eb has been observed above the band crossing. In the band crossing region the SD transitions are retarded, an effect which has been observed for the first time in the A ≈ 150 region. It may indicate a reduction of the quadrupole moment below the crossing as expected from theoretical calculations. (Supported by the BMBF and the KBN).
[1] S. Lunardi et al., Phys. Rev. Lett. 72, 1427 (1994)