Abstract
An enhanced low-energy electric dipole () strength is identified for the weakly bound excited states of the neutron-rich isotope . The Doppler-shift lifetime measurements employing a combination of the -ray tracking array GRETINA, the plunger device, and the S800 spectrograph determine the lower limit of or 0.052 W.u. for the transition in , representing one of the strongest strengths observed among the bound discrete states in this mass region. This value is at least 30 times larger than that measured for the decay to the ground state. A comparison of the present results to large-scale shell-model calculations points to an important role of core excitations and deformation in the observed enhancement, suggesting a novel example of the electric dipole modes manifested in weakly bound deformed systems.
- Received 25 July 2018
- Revised 7 November 2018
DOI:https://doi.org/10.1103/PhysRevLett.121.262501
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