Abstract
Two fusion-fission experiments have been performed and studied with the Euroball Ge array: 12 C + 238 U at 90MeV bombarding energy, and 18 O + 208 Pb at 85MeV. Among the lot of new information extracted during the last decade, the latest results discussed here are the discovery of the high-spin states of 119-126 Sn. The maximum value of angular momentum available in the νh11/2 shell, i.e. for mid-occupation and the breaking of the three neutron pairs (seniority v = 6), has been identified in several tin isotopes. It is the first time that such high-seniority states are established in spherical nuclei.
Highlights
In addition to deep inelastic collisions, the fission process is a very convenient tool to produce a large number of neutron-rich isotopes in a single experiment
Our new results concerning the tin isotopes are discussed in this paper
Pure j n configurations occur in a very few nuclei, since an orbit j is rarely bounded by two gaps in energy, and the closeness of several orbits leads to configuration mixings
Summary
In addition to deep inelastic collisions, the fission process (either spontaneous or induced by heavy ions) is a very convenient tool to produce a large number of neutron-rich isotopes in a single experiment. The high-spin states of the Sn isotopes do contain a large ν(h11/2)n component, since the two other valence orbits, νs1/2 and νd3/2, cannot afford large spin values Such a work is restricted to N ≥ 70 since the yrast states of the lightest Sn isotopes are dominated by a collective band coming from two-particle-two-hole excitations across the Z = 50 gap; and the states coming from the ν(h11/2)n cannot be identified. The medium spin states of the 120–126Sn isotopes were only measured up to the spin I = 10+ for the even mass and I = 27/2− for the odd mass, by using reactions induced by light ions, deep inelastic reactions, isomeric decays of long-lived states of Sn produced by fission of actinides, or -decays of the high-spin long-lived states of heavy indium nuclei [2,3,4,5,6,7,8]. The maximum value of angular momentum available in this high-j shell, i.e. for mid-occupation and the breaking of the three pairs, has been identified [10]
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