Elsevier

Nuclear Physics A

Volume 439, Issue 3, 17 June 1985, Pages 573-588
Nuclear Physics A

Feeding times of high-spin states in 152, 154Dy: Probes of nuclear structure above the yrast line

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Abstract

Measurements of feeding times of high-spin yrast states up to spin 30 ℏ in 154Dy and 36 ℏ in 152 Dy were utilized to obtain information about possible spin-dependent shape changes. The reactions 25Mg(134Xe, 5n), 124Sn(34S, 4n) and 25Mg(132Xe, 5n), 122Sn(34S, 4n) were used to populate the high-spin states in 154Dy and 152Dy, respectively. Feeding times as well as lifetimes were determined with the recoil-distance technique. In 152Dy only long feeding times (⩾ 10 ps) could be identified, indicating that the aligned-particle yrast states are fed through configurations of similar character, with little direct population from collective cascades in the continuum region. In 154Dy discrete states with I ⩽ 30 ℏ have lifetimes which are characteristically collective, whereas the preyrast cascades exhibit both fast (≲1 ps) and slow (∼10 ps) feeding components. The latter imply a change with increasing spin from collective to aligned-particle character, probably associated with a prolate to oblate shape transition.

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Permanent address: Université Catholique de Louvain, B-1348 Louvain-La-Neuve, Belgium.

∗∗

Present address: Reactor Research Center, Kalpakkam, India.

∗∗∗

Present address: TRIUMF, Vancouver, Canada.

Permanent address: University of Jyväskylä, Jyväskylä, Finland.

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