Lifetime measurements of excited states in 169,171,173 Os: persistence of anomalous B(E2) ratios in transitional rare earth nuclei in the presence of a decoupled i13/2 valence neutron

W. Zhang*, B. Cederwall, M. Doncel, Ö. Aktas, A. Ertoprak, R. Liotta, C. Qi, T. Grahn, B.S. Nara Singh, D.M. Cullen, D. Hodge, M. Giles, S. Stolze, H. Badran, T. Braunroth, T. Calverley, D.M. Cox, Y.D. Fang, P.T. Greenlees, J. HiltonE. Ideguchi, R. Julin, S. Juutinen, M. Kumar Raju, H. Li, H. Liu, S. Matta, P. Subramaniam, V. Modiamo, J. Pakarinen, P. Papadakis, J. Partanen, C.M. Petrache, P. Rahkila, P. Ruotsalainen, M. Sandzelius, J. Sarén, C. Scholey, J. Sorri, M.J. Taylor, J. Uusitalo, J.J. Valiente-Dobón

*Corresponding author for this work

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Lifetimes of low-lying excited states in the vi13/2+ bands of the neutron-deficient osmium isotopes 169,171,173Os have been measured for the first time using the recoil-distance Doppler shift and recoil-isomer tagging techniques. An unusually low value is observed for the ratio B(E2; 21/2+ ->17/2+)/B(E2; 17/2+ -> 13/2+) in 169Os, similarly to the \anomalously" low values of the ratio B(E2; 4+1-> 2+1)/B(E2; 2+1-> 0+gs) previously observed in several transitional rare-earth nuclides with even numbers of neutrons and protons, including the neighboring 168,170Os. Furthermore, the evolution of B(E2; 21/2+ ->17/2+)/B(E2; 17/2+ -> 13/2+) with increasing neutron number in the odd-mass isotopic chain 169,171,173Os is observed to follow the same trend as observed previously in the even-even Os isotopes. These findings indicate that the possible quantum phase transition from
a seniority conserving structure to a collective regime as a function of neutron number suggested for the even-even systems is maintained in these odd-mass osmium nuclei, with the odd valence neutron merely acting as a "spectator". As for the even-even nuclei, the phenomenon is highly unexpected for nuclei that are not situated near closed shells.
Original languageEnglish
Article number136527
Number of pages9
JournalPhysics Letters B
Early online date22 Jul 2021
Publication statusPublished - 10 Sep 2021


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