Abstract
Lifetime measurements of excited states of the light isotones , , and have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities and were obtained for the first time for the hard-to-reach . While the values of , saturate the maximum quadrupole collectivity offered by the natural valence (, , , ) space of an inert core, the value obtained for largely exceeds it, suggesting that shape coexistence phenomena, previously reported at , extend beyond . The onset of collectivity at is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector field in shell-structure evolution.
- Received 18 May 2018
- Revised 27 August 2018
DOI:https://doi.org/10.1103/PhysRevLett.121.192502
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society