The Tz=-32 nucleus Mg21 has been studied by Coulomb excitation on Pt196 and Pd110 targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 52+ ground state to the first excited 12+ state in Mg21 was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the 12+ state yield an adopted value of B(E2;52+→12+)=13.3(4) W.u. A new excited state at 1672(1) keV with tentative 92+ assignment was also identified in Mg21. This work demonstrates a large difference in the B(E2;52+→12+) value between T=32, A=21 mirror nuclei. The difference is investigated in the shell-model framework employing both isospin conserving and breaking USD interactions and using modern ab initio nuclear structure calculations, which have recently become applicable in the sd shell.
Publication Source (Journal or Book title)
Physical Review C
Ruotsalainen, P., Henderson, J., Hackman, G., Sargsyan, G., Launey, K., Saxena, A., Srivastava, P., Stroberg, S., Grahn, T., Pakarinen, J., Ball, G., Julin, R., Greenlees, P., Smallcombe, J., Andreoiu, C., Bernier, N., Bowry, M., Buckner, M., Caballero-Folch, R., Chester, A., Cruz, S., Evitts, L., Frederick, R., Garnsworthy, A., Holl, M., Kurkjian, A., Kisliuk, D., Leach, K., McGee, E., Measures, J., Mücher, D., Park, J., & Sarazin, F. (2019). Isospin symmetry in B(E2) values: Coulomb excitation study of Mg 21. Physical Review C, 99 (5) https://doi.org/10.1103/PhysRevC.99.051301