Speaker
Description
At the limit of stability, atomic nuclei can exhibit unique structure due to the proximity to the particle-
decay threshold. In particular, if orbitals near the Fermi surface have low angular momenta, they can
induce spatially extended wave functions for valence neutrons, forming nuclear halo. In light p and psd
shells, halo nuclei have so far served as a benchmark for understanding of nuclear structure and
dynamics of weakly-bound systems. However, for an unexplored heavier-mass neutron-rich region, halo
formation and excitation properties can be more extensive than hitherto expected due to increasing
degrees of collectivity and correlations.
As a way to investigate the dynamics of neutron-rich weakly-bound systems, we have performed
excited-state lifetime measurements on neutron-rich C and Ne isotopes [1,2,3]. The experiments were
performed utilizing the combination of fast beams of rare isotopes, GRETINA, TRIPLEX plunger device
and S800 Spectrograph. Experimentally extracted transition probabilities are used to characterize the
electromagnetic responses of weakly-bound states through comparison with data available in
neighboring nuclei as well as theoretical calculations. Examples of our recent results include an
unexpectedly large E1 strength discovered in the neutron-rich 27 Ne isotope [2] as well as an enhanced E2
strength observed for the 29 Ne isotope in the vicinity of N=20 [3].
The experimental results will be presented and discussed in terms of an interplay between the shell
erosion, deformation, and weakly bound nature of nuclei far from stability. Perspectives for ongoing and
future studies at FRIB will also be discussed.
[1] K.Whitmore et al., Phys. Rev. C 91, 041303(R), (2015)
[2] C.Loelius et al., Phys. Rev. Lett. 121, 262501, (2018)
[3] A.Revel et al., Phys. Lett. B838, 137704, (2023)
