Nature of seniority symmetry breaking in the semimagic nucleus 94Ru

B. Das*, B. Cederwall*, C. Qi, M. Górska, P. H. Regan, Ö. Aktas, H. M. Albers, A. Banerjee, M. M. R. Chishti, J. Gerl, N. Hubbard, S. Jazrawi, J. Jolie, A. K. Mistry, M. Polettini, A. Yaneva, S. Alhomaidhi, J. Zhao, T. Arici, S. BagchiG. Benzoni, P. Boutachkov, T. Davinson, T. Dickel, E. Haettner, O. Hall, Ch Hornung, J. P. Hucka, P. R. John, I. Kojouharov, R. Knöbel, D. Kostyleva, N. Kuzminchuk, I. Mukha, W. R. Plass, B. S. Nara Singh, J. Vasiljević, S. Pietri, Zs. Podolyak, M. Rudigier, H. Rösch, E. Sahin, H. Schaffner, C. Scheidenberger, F. Schirru, A. Sharma, R. Shearman, Y. Tanaka, J. Vesić, H. Weick, H. J. Wollersheim, U. Ahmed, A. Algora, C. Appleton, J. Benito, A. Blazhev, A. Bracco, A. M. Bruce, M. Brunet, R. Canavan, A. Esmaylzadeh, L. M. Fraile, G. Häfner, H. Heggen, D. Kahl, V. Karayonchev, R. Kern, A. Korgu, G. Kosir, N. Kurz, R. Lozeva, M. Mikolajczuk, P. Napiralla, R. Page, C. M. Petrache, N. Pietralla, J.-M. Régis, P. Ruotsalainen, L. Sexton, V. Sanchez-Temble, M. Si, J. Vilhena, V. Werner, J. Wiederhold, W. Witt, P. J. Woods, G. Zimba

*Corresponding author for this work

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Direct lifetime measurements via γ−γ coincidences using a fast timing detector array consisting of LaBr3(Ce) scintillators has been applied to determine the lifetime of low-lying states in the semimagic (N=50) nucleus 94Ru. The experiment was carried out as the first in a series of “FAIR-0” experiments with the DESPEC experimental setup at the Facility for Antiproton and Ion Research (FAIR). Excited states in 94Ru were populated primarily via the β-delayed proton emission of 95Pd nuclei, produced in the projectile fragmentation of an 850 MeV/nucleon 124Xe beam impinging on a 4 g/cm2 9Be target. While the deduced E2 strength for the2+→0+ transition in the yrast cascade follows the expected behavior for conserved seniority symmetry, the intermediate 4+→2+ transition exhibits a drastic enhancement of transition strength in comparison with pure-seniority model predictions as well as standard shell model predictions in the fpg proton hole space with respect to doubly magic 100Sn. The anomalous behavior is ascribed to a subtle interference between the wave function of the lowest seniority ν=2, Iπ=4state and that of a close-lying ν=4 state that exhibits partial dynamic symmetry. In addition, the observed strongly prohibitive 6+→4+transition can be attributed to the same mechanism but with a destructive interference. It is noted that such effects may provide stringent tests of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations.
Original languageEnglish
Article numberL031304
Number of pages6
JournalPhysical Review C
Issue number3
Publication statusPublished - 25 Mar 2022


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