Hexadecapole strength in the rare isotopes 74,76Kr

In the Ge-Sr mass region, isotopes with neutron number N <= 40 are known to feature rapid shape changes with both nucleon number and angular momentum. To gain new insights into their structure, inelastic proton scattering experiments in inverse kinematics were performed on the rare isotopes 74,76Kr. This work focuses on observables related to the J pi = 4+1 states of the Kr isotopes and, in particular, on the hexadecapole degree of freedom. By performing coupled-channels calculations, hexadecapole deformation parameters /34 were determined for the J pi = 4+1 states of 74,76Kr from inelastic proton scattering cross sections. Two possible coupled-channels solutions were found. A comparison to predictions from nuclear energy density functional theory, employing both non-relativistic and relativistic functionals, clearly favors the large, positive /34 solutions. These /34 values are unambiguously linked to the well deformed prolate configuration. Given the /32 - /34 trend, established in this work, it appears that /34 values could provide a sensitive measure of the nuclear shell structure.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.

Automated summary

Inelastic proton scattering experiments in inverse kinematics were performed on the rare isotopes 74,76Kr to study their structure. The focus was on the J pi = 4+1 states and the hexadecapole degree of freedom. By performing coupled-channels calculations, deformation parameters /34 for the Kr isotopes were determined, and two possible solutions were found. Comparisons to predictions from nuclear energy density functional theory favored large, positive /34 solutions, which are linked to well deformed prolate configurations. The /34 values may serve as sensitive measures of the nuclear shell structure.