Abstract
The transition matrix elements of isobaric multiplets are expected to follow a linear trend as a function of isospin projection. However, measurements of the transitions in the triplet of Ca, K, and Ar show a deviation from this trend with an enhanced transition strength in with respect to its mirror . We have studied analogue transitions in and its mirror partner to determine if this enhancement persists in neighboring Ca isotopes. Recoil-distance lifetime measurements of and were performed utilizing a secondary beam, the TRIPLEX plunger, the GRETINA array, and the S800 spectrograph. Our data provide a lifetime measurement of the () state in as well as an improved lifetime result for the () state, while the data are used to validate the present analysis. A comparison of the present data to shell-model calculations suggests an enhanced transition strength in , pointing to both proton and neutron contributions to core excitations across the shell gaps in close proximity to .
1 More- Received 29 May 2024
- Accepted 8 August 2024
DOI:https://doi.org/10.1103/PhysRevC.110.024322
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