Eur. Phys. J. A 10, 13-19

New excited superdeformed bands in heavy nuclei: Clue for an octupole softness near the gap at large deformation

A. Prévost¹, N. Buforn¹, A. Astier¹, R. Duffait¹, M. Meyer¹, S. Perriès¹, N. Redon¹, O. Stézowski¹, A. Bauchet², I. Deloncle², M.G. Porquet², A. Görgen³, H. Hübel³, E. Mergel³, S. Neumann³, D. Roßbach³, N. Nenoff³, G. Schönwaßer³, A.N. Wilson⁴, R. Lucas⁵, F.A. Beck⁶, D. Curien⁶, G. Duchêne⁶, B.J.P. Gall⁶, N. Kintz⁶, J.P. Vivien⁶ and D.M. Cullen<sup>7

1</sup>  IPN Lyon, IN2P3/CNRS, Université Lyon-1, F-69622 Villeurbanne Cedex, France
²  CSNSM Orsay, IN2P3/CNRS, Université Paris-Sud, F-91405 Orsay Campus, France
³  Institut für Strahlen- und Kernphysik, Universität Bonn, Nussallee 14-16, D-53115 Bonn, Germany
⁴  Department of Physics, University of York, York Y01 5DD, United Kingdom
⁵  CEA/Saclay, DAPNIA/SPhN, F-91191 Gif sur Yvette, France
⁶  IReS Strasbourg, IN2P3/CNRS, Université Louis Pasteur, F-67037 Strasbourg Cedex 2, France
⁷  Oliver Lodge Laboratory, Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom

astier@ipnl.in2p3.fr

(Received: 20 December 2000 Communicated by D. Schwalm )

Abstract
We report the identification of six new superdeformed (SD) bands in ^197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals and confirm indirectly a N=118 SD gap.

PACS
21.10.Re - Collective levels.
21.60.Ev - Collective models.
23.20.Lv - Gamma transitions and level energies.
27.80.+w - 190 .

© Società Italiana di Fisica, Springer-Verlag 2001