Quantum tunneling of the excited rotational bands in the superdeformed nucleus Eu-143

The properties of the thermally excited rotational motion up to the region of rotational damping are studied experimentally in the superdeformed nucle us Eu-143. Th, effective lifetime of the excited discrete rotational hands forming ridge structures in gamma-gamma matrices is measured at the EUROBAL L array using the DSAM technique, giving a quadrupole moment Q(t) approxima te to 10 eb, consistent with the deformation of the superdeformed yrast ban d. In addition, the effective number of excited superdeformed bands is extr acted by a statistical analysis of the ridge structure, for transition ener gies down to the region where the effect of the decay-out into the normal d eformed well shows up. The experimental data are compared with microscopic cranked shell model calculations including a residual interaction of surfac e delta type. Satisfactory agreement between data and theory is obtained wh en the quantum tunneling of the excited superdeformed states is included in the model. (C) 2001 Published by Elsevier Science B.V.