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4 páginas, 4 figuras.-- El Pdf es la versión pre-print.-- et al. ; Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin–orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron–proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron–proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis. ; This work was supported by the Swedish Research Council (contract nos 2007-4067 and 2008-5793), the Göran Gustafsson Foundation, the European Union Sixth Framework Programme 'Integrating Infrastructure Initiative – Transnational Access' (no. 506065; EURONS), the Hungarian Scientific Research Fund, OTKA (contract nos. K72566 and K68801), the UK Science and Technology Facilities Council (STFC), the Polish Ministry of Science and Higher Education (grant no. N N202 073935), the Spanish Ministerio de Ciencia e Innovación (contract no. FPA2007-66069), the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042), and Ankara University BIYEP project no. DPT 2005120140. ; Peer reviewed

WOS:000513242500002 ; The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide Ru-88(44)44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in Ru-88 were populated via the Fe-54(Ar-36, 2n gamma)Ru-88* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. The observed gamma-ray cascade is assigned to Ru-88 using clean prompt gamma-gamma-2-neutron coincidences in anticoincidence with the detection of charged particles, confirming and extending the previously assigned sequence of low-lying excited states. It is consistent with a moderately deformed rotating system exhibiting a band crossing at a rotational frequency that is significantly higher than standard theoretical predictions with isovector pairing, as well as observations in neighboring N > Z nuclides. The direct observation of such a "delayed" rotational alignment in a deformed N = Z nucleus is in agreement with theoretical predictions related to the presence of strong isoscalar neutron-proton pair correlations. ; Swedish Research CouncilSwedish Research Council [621-2014-5558]; EU 7th Framework Programme, Integrating Activities Transnational AccessEuropean Union (EU) [262010 ENSAR]; United Kingdom STFCScience & Technology Facilities Council (STFC) [ST/L005727/1, ST/P003885/1]; Polish National Science Centre [2017/25/B/ST2/01569, 2016/22/M/ST2/00269, 2014/14/M/ST2/00738]; COPIN-INFN collaboration; COPIN-IN2P3; COPIGAL projects; National Research Development and Innovation Fund of Hungary [K128947]; European Regional Development FundEuropean Union (EU) [GINOP-2.3.3-15-2016-00034]; Hungarian National Research, Development and Innovation Office [PD124717]; Ministry of Science, Spain [SEV-2014-0398, FPA2017-84756-C4]; EU FEDER fundsEuropean Union (EU); China Scholarship CouncilChina Scholarship Council [201700260183] ; This work was supported by the Swedish Research Council under Grant No. 621-2014-5558 and the EU 7th Framework Programme, Integrating Activities Transnational Access, Grant No. 262010 ENSAR; the United Kingdom STFC under Grants No. ST/L005727/1 and No. ST/P003885/1; the Polish National Science Centre, Grants No. 2017/25/B/ST2/01569, No. 2016/22/M/ST2/00269, No. 2014/14/M/ST2/00738 (COPIN-INFN collaboration; COPIN-IN2P3 and COPIGAL projects; the National Research Development and Innovation Fund of Hungary (Grant No. K128947); the European Regional Development Fund (Contract No. GINOP-2.3.3-15-2016-00034), by the Hungarian National Research, Development and Innovation Office, Grant No. PD124717; the Ministry of Science, Spain, under Grants No. SEV-2014-0398 and FPA2017-84756-C4; and by the EU FEDER funds. X. L. gratefully acknowledges support from the China Scholarship Council, Grant No. 201700260183 for his stay in Sweden. We thank the GANIL staff for excellent technical support and operation.

13 pags., 12 figs., 4 tabs. ; Transition probabilities of intermediate-spin yrast and non-yrast excitations in Se80,82 were investigated in a recoil distance Doppler-shift (RDDS) experiment performed at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. The Cologne Plunger device for deep inelastic scattering was used for the RDDS technique and was combined with the AGATA Demonstrator array for the γ-ray detection and coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In Se80, the level lifetimes of the yrast (61+) and (81+) states and of a non-yrast band feeding the yrast 41+ state are determined. A spin and parity assignment of the head of this sideband is discussed based on the experimental results and supported by large-scale shell-model calculations. In Se82, the level lifetimes of the yrast 61+ state and the yrare 42+ state and lifetime limits of the yrast (101+) state and of the 51- state are determined. Although the experimental results contain large uncertainties, they are interpreted with care in terms of large-scale shell-model calculations using the effective interactions JUN45 and jj44b. The excited states' wave functions are investigated and discussed with respect to the role of the neutron g9/2 orbital. ; This work was partially supported by the European Union Seventh Framework Program FP7/2007-2013 under Grant Agreement No. 262010 ENSAR, by the German Research Foundation (DFG) under Contract No. DE 1516/3-1, by the German BMBF under Grant No. 05P15PKFNA and by the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5-4-P. J.L. and A.V. thank the Bonn-Cologne Graduate School of Physics and Astronomy (BCGS) for financial support. ; Peer Reviewed

WOS: 000350998600002 ; The level structure of the neutron-rich Cu-69, Cu-71, and Cu-73 isotopes has been investigated by means of multinucleon transfer reactions. The experiment was performed at Laboratori Nazionali di Legnaro using the AGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states in Cu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrix elements for transitions from excited states in Cu-69,Cu-71,Cu-73 nuclei are used to assess the collective or single-particle character of these states. The results are compared with predictions of large-scale shell-model calculations, giving further insight into the evolution of the proton pf shell as neutrons fill the 1g(9/2) orbital. ; European Union Seventh Framework Program FP7 [262010]; ENSAR; MINECO, Spain [FPA2011-29854-C03, FPA2011-29854-C04, Consolider-Ingenio 2010 CSD2007-00042]; Generalitat Valenciana, Spain [PROMETEOII/2014/019] ; This work has been partially supported by the European Union Seventh Framework Program FP7/2007-2013 under Grant Agreement No. 262010, ENSAR and MINECO, Spain, under Grants No. FPA2011-29854-C03 and No. FPA2011-29854-C04, Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019, and MINECO, Spain, under Grant Consolider-Ingenio 2010 CSD2007-00042.