Lifetime Measurements of Excited States in Pt 172 and the Variation of Quadrupole Transition Strength with Angular Momentum
Year: 2018
Type: article
Abstract: Lifetimes of the first excited 2^{+} and 4^{+} states in the extremely neutron-deficient nuclide ^{172}Pt have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+})=0.55(19) was found, similar to a handful of other such anomalous cases observed in the entire Segré chart. The observation adds to a cluster of a few extremely neutron-deficient nuclides of the heavy transition metals with neutron numbers N≈90-94 featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers N≈90-94 reveal a quantum phase transition from a seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.
Source: Physical Review Letters
Authors: B. Cederwall, M. Doncel, Ö. Aktas, A. Ertoprak, R. Liotta, C. Qi, T. Grahn, 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. Hilton, E. Ideguchi, R. Julin, S. Juutinen, M. Kumar Raju, H. Li, H. Liu, S. Matta, V. Modamio, J. Pakarinen, P. Papadakis, J. Partanen, C. M. Petrache, P. Rahkila, P. Ruotsalainen, M. Sandzelius, J. Sarén, C. Scholey, J. Sorri, P. Subramaniam, M. J. Taylor, J. Uusitalo, J. J. Valiente-Dobón
Institutions: KTH Royal Institute of Technology, University of Liverpool, Istanbul University, University of Jyväskylä, University of Manchester, University of Cologne, Research Center for Nuclear Physics, The University of Osaka, The University of Osaka, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Institut National de Physique Nucléaire et de Physique des Particules, Grand Accélérateur National d'Ions Lourds, University of Oslo, Université Paris-Saclay, Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro
Language: Latvian
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: Manchester Experimental Nuclear Physics Consolidated Grant Request 2011, G3108416639, G344218824, Manchester Nuclear Physics Consolidated Grant Request, G385191638, G4654319827, Determining the role of non-axial deformation on proton decays; DPUNS - A Differential Plunger for Unbound Nuclear States., Nuclear structure near the limits of stability, G6065244595, Nuclear Physics Consolidated Grant 2013, G777192503, G8683243488
OpenAlex ID: W2809490331