Physics Letters B
Volume 760, 10 September 2016, Pages 273–278
The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus 133Sb
G. Bocchia, b, S. Leonia, b, , , B. Fornalc, G. Colòa, b, P.F. Bortignona, b, S. Bottonia, b, A. Braccoa, b, C. Michelagnolid, D. Bazzaccoe, A. Blancf, G. de Franced, M. Jentschelf, U. Kösterf, P. Muttif, J.-M. Régisg, G. Simpsonh, T. Soldnerf, C.A. Ure, i, W. Urbanj, L.M. Frailek, R. Lozeval, B. Belvitoa, b, G. Benzonib, A. Brucem, R. Carrolln, N. Cieplicka-Oryǹczakb, c, F.C.L. Crespia, b, F. Didierjeanl, J. Jolieg, W. Korteno, T. Kröllp, S. Lalkovskin, q, H. Machk, N. Mărgineanr, B. Melons, D. Mengonie, t, B. Millionb, A. Nanninis,
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Abstract
The γ-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between γ-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 μs isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, revealed a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.
Keywords
- Neutron induced fission;
- Gamma spectroscopy;
- Nuclear state lifetime;
- Large Ge array;
- Particle-core couplings
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