Lifetime measurements of excited states in <sup>169,171,173</sup>Os : persistence of anomalous <em>B</em>(<em>E</em>2) ratios in transitional rare earth nuclei in the presence of a decoupled <em>i</em><sub>13/2</sub> valence neutron
Zhang, W.; Cederwall, B.; Doncel, M.; Aktas, O.; Ertoprak, A.; Liotta, R.; Qi, C.; Grahn, T.; Singh, B. S. Nara; Cullen, D. M.; Hodge, D.; Giles, M.; Stolze, S.; Badran, H.; Braunroth, T.; Calverley, T.; Cox, D. M.; Fang, Y. D.; Greenlees, P. T.; Hilton, J.; Ideguchi, E.; Julin, R.; Juutinen, S.; Raju, M. Kumar; Li, H.; Liu, H.; Matta, S.; Subramaniam, P.; Modamio, V; Pakarinen, J.; Papadakis, P.; Partanen, J.; Petrache, C. M.; Rahkila, P.; Ruotsalainen, P.; Sandzelius, M.; Saren, J.; Scholey, C.; Sorri, J.; Taylor, M. J.; Uusitalo, J.; Valiente-Dobon, J. J. (2021-07-27)
Zhang, W., Cederwall, B., Doncel, M., Aktas, Ö., Ertoprak, A., Liotta, R., Qi, C., Grahn, T., Nara Singh, B. S., Cullen, D. M., Hodge, D., Giles, M., Stolze, S., Badran, H., Braunroth, T., Calverley, T., Cox, D. M., Fang, Y. D., Greenlees, P. T., … Valiente-Dobón, J. J. (2021). Lifetime measurements of excited states in 169,171,173Os: Persistence of anomalous B(E2) ratios in transitional rare earth nuclei in the presence of a decoupled i13/2 valence neutron. Physics Letters B, 820, 136527. https://doi.org/10.1016/j.physletb.2021.136527
© 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2022033026210
Tiivistelmä
Abstract
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, similar 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.
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