Broken seniority symmetry in the semimagic proton mid-shell nucleus Rh 95

• Published in: Physical review research 2024-05, Vol.6 (2), Article L022038
• Main Authors: Das, B., Cederwall, B., Qi, C., Górska, M., Regan, P. H., Aktas, Ö., Albers, H. M., Banerjee, A., Chishti, M. M. R., Gerl, J., Hubbard, N., Jazrawi, S., Jolie, J., Mistry, A. K., Nowacki, F., Polettini, M., Yaneva, A., Ahmed, U., Alhomaidhi, S., Algora, A., Appleton, C., Arici, T., Bagchi, S., Benzoni, G., Benito, J., Blazhev, A., Boutachkov, P., Bracco, A., Bruce, A. M., Brunet, M., Canavan, R., Davinson, T., Dickel, T., Esmaylzadeh, A., Fraile, L. M., Haettner, E., Hall, O., Häfner, G., Heggen, H., Hornung, Ch, Hucka, J. P., John, P. R., Kahl, D., Karayonchev, V., Kern, R., Knöbel, R., Korgul, A., Kosir, G., Kojouharov, I., Kostyleva, D., Kuzminchuk, N., Kurz, N., Liotta, R., Lozeva, R., Mikolajczuk, M., Mukha, I., Napiralla, P., Page, R., Petrache, C. M., Pietralla, N., Pietri, S., Plaß, W. R., Podolyák, Zs, Régis, J.-M., Rudigier, M., Rösch, H., Ruotsalainen, P., Sahin, E., Sánchez-Tembleque, V., Schaffner, H., Scheidenberger, C., Schirru, F., Sexton, L., Singh, B. S. Nara, Sharma, A., Shearman, R., Si, M., Tanaka, Y. K., Vasiljević, J., Vesić, J., Vilhena, J., Weick, H., Wollersheim, H. J., Werner, V., Wiederhold, J., Witt, W., Woods, P. J., Zimba, G., Zhao, J.
• Format: Article
• Language: English
• ISSN: 2643-1564; 2643-1564
• DOI: 10.1103/PhysRevResearch.6.L022038

Lifetime measurements of low-lying excited states in the semimagic ( N = 50 ) nucleus Rh 95 have been performed by means of the fast-timing technique. The experiment was carried out using γ -ray detector arrays consisting of LaBr 3 (Ce) scintillators and germanium detectors integrated into the DESPEC experimental setup commissioned for the Facility for Antiproton and Ion Research () Phase-0, Darmstadt, Germany. The excited states in Rh 95 were populated primarily via the β decays of Pd 95 nuclei, produced in the projectile fragmentation of a 850 MeV/nucleon Xe 124 beam impinging on a 4 g / cm 2 Be 9 target. The deduced electromagnetic E2 transition strengths for the γ -ray cascade within the multiplet structure depopulating from the isomeric I π = 21 / 2 + state are found to exhibit strong deviations from predictions of standard shell model calculations which feature approximately conserved seniority symmetry. In particular, the observation of a strongly suppressed E2 strength for the 13 / 2 + → 9 / 2 + ground state transition cannot be explained by calculations employing standard interactions. This remarkable result may require revision of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations, and might also point to the need for including three-body forces in the Hamiltonian.