Unpaired band crossings in the A similar to 160 mass region

J C Lisle, J Simpson, A P Bagshaw, M A Bentley, D M Cullen, P J Dagnall, G B Hagemann, S L Kings, D Napoli, M Riley, S Shepherd, A G Smith, S Tormanen

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    Levels schemes for a number of low lying normally deformed bands in Er-161,Er-162 have been extended to significantly higher spins than hitherto using the EUROBALL Ge detector array sited at the Legnaro National Laboratory. In the case of one band in Er-161 states have tentatively been observed to a spin in excess of 60 (h) over bar. Evidence is found for a band crossing at high spin in the yrast even parity, positive signature (+,+1/2) band in Er-161. This can be explained in terms of a system in which the static pairing is quenched either involving a rearrangement of two neutrons into steeply aligning i(13/2) orbitals or possibly an interchange of state of one proton and one neutron. A similar type of band crossing is tentatively identified in the lowest (-,-1/2) band of Er-161. Since a crossing involving the interchange of neutrons is blocked, this must involve protons. This, if confirmed, provides the first direct evidence for the quenching of static proton pairing at high spin in this mass region. Recent calculations [1] predict that such a crossing involving purely protons will occur in this band at I similar to 60 (h) over bar.
    Original languageEnglish
    JournalAIP Conference Proceedings
    Publication statusPublished - 1999


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