High Spin Physics 2001, Warsaw, February 6-10, 2001



Abstract No: 019
Submitted on: 29 Dec 2000, 12:57 GMT
Title: New superdeformed and "high spin" structures in the A=80-100 and A=150 regions.
Author(s): A. Johnson,1
Affiliation(s): 1 Department of Physics, Royal Institute of Technology, Stockholm, Sweden



New, highly effective arrays for $\gamma$-ray spectroscopy like EUROBALL and Gammasphere, combined with state of the art ancillary detectors and/or recoil mass separators for channel selection, have during recent years allowed identification and in-beam $\gamma$-spectroscopic studies of very neutron deficient nuclei in the $A\approx80-100$ mass region. These nuclei have so far been produced in heavy-ion induced fusion evaporation reactions utilizing stable beams and targets. This mass region shows a richness of phenomena. Here the heaviest N=Z nuclei are identified and enhanced neutron-proton correlations are expected when protons and neutrons occupy identical orbitals. At the same time the vicinity to the proton drip line may influence the stability and structure of the most neutron deficient nuclei. The nucleus 100Sn is the heaviest N=Z doubly magic nucleus believed to be bound. 100Sn and its neighbours are key nuclei for understanding the nuclear shell model. New "high spin" results on some neighbours of 100Sn will be presented.

The A=80-90 region was early predicted to be a favoured region for observation of superdeformed (SD) structures. A number of SD-bands have been reported for nuclei with A=80-91. Large energy gaps at SD-shapes for especially N=Z=38,42,44,46 stabilize the structures. The N=Z nucleus 88Ru is predicted to have a ``doubly magic'' SD structure with two protons and two neutrons in the lowest N=5 intruder orbitals. Recently SD structures have been reported for 88Mo [1], 89Tc [2] and 91Tc [3] which are the heaviest nuclei in this region with known SD-structures. The SD-band in 91Tc shows unexpected features. The SD-structures of these nuclei will be discussed.

In 154Er a new SD-band has been observed in an experiment at EUROBALL [4]. The structure of this new band and the previously observed SD-band in 154Er will be discussed.

Bibliography

1
T.Bäck et al., Eur. Phys. J.A6, 391 (1999).

2
B.Cederwall et al., Eur. Phys. J.A6, 251 (1999).

3
E.Ideguchi et al. Phys. Lett. B492, 245 (2000).

4
K.Lagergren et al. , to be published.

\fbox{ Invited talk. }

High Spin Conference
2000-12-29