# First Measurement of the *B*(*E*2;3/2^{−}→1/2^{−}) Transition Strength in ^{7}Be: Testing *Ab Initio* Predictions for A=7 Nuclei

Published in *Physical Review C*, 2019

DOI: 10.1103/PhysRevC.99.064320 | arXiv: 2109.07312

Recommended citation: S. L. Henderson, T. Ahn, M. A. Caprio, P. J. Fasano, et al., Phys. Rev. C 99, 064320 (2019). __(download)__

Electromagnetic observables are able to give insight into collective and emergent features in nuclei, including nuclear clustering. These observables also provide strong constraints for *ab initio* theory, but comparison of these observables between theory and experiment can be difficult due to the lack of convergence for relevant calculated values, such as $E2$ transition strengths. By comparing the ratios of $E2$ transition strengths for mirror transitions, we find that a wide range of *ab initio* calculations give robust and consistent predictions for this ratio. To experimentally test the validity of these *ab initio* predictions, we performed a Coulomb excitation experiment to measure the $B(E2;3/2^− \rightarrow 1/2^−)$ transition strength in ^{7}Be for the first time. A $B(E2;3/2^− \rightarrow 1/2^−)$ value of 26(6)_{stat}(3)_{syst} *e*^{2} fm^{4} was deduced from the measured Coulomb excitation cross section. This result is used with the experimentally known ^{7}Li $B(E2;3/2^− \rightarrow 1/2^−)$ value to provide an experimental ratio to compare with the *ab initio* predictions. Our experimental value is consistent with the theoretical ratios within $1\sigma$ uncertainty, giving experimental support for the value of these ratios. Further work in both theory and experiment can give insight into the robustness of these ratios and their physical meaning.