Suchergebnisse

18 pags., 10 figs., 4 tabs. ; The β- decay of Zn81 to the neutron magic N=50 nucleus Ga81, with only three valence protons with respect to Ni78, was investigated. The study was performed at the ISOLDE facility at CERN by means of γ spectroscopy. The Zn81 half-life was determined to be T1/2=290(4) ms while the β-delayed neutron emission probability was measured as Pn=23(4)%. The analysis of the β-gated γ-ray singles and γ-γ coincidences from the decay of Zn81 provides 47 new levels and 70 new transitions in Ga81. The β-n decay of Zn81 was observed and a new decay scheme into the odd-odd Ga80 nucleus was established. The half-lives of the first and second excited states of Ga81 were measured via the fast-timing method using LaBr3(Ce) detectors. The level scheme and transition rates are compared to large-scale shell-model calculations. The low-lying structure of Ga81 is interpreted in terms of the coupling of the three valence protons outside the doubly magic Ni78 core. ; This work was supported by the Spanish MINECO through the FPA2015-65035-P and RTI2018-098868-B-I00 projects, by the U.S. DoE Grant No. DE-FG02-94ER40834, by the German BMBF Grant 05P19PKFNA, and Grupo de Física Nuclear (GFN) at UCM. The support by the European Union Seventh Framework through ENSAR (Contract No. 262010) and ISOLDE (CERN) Collaboration is acknowledged. V.P. acknowledges support by the Spanish FPI-BES-2011-045931 grant.

12 pags., 8 figs., 1 tab. ; The structure of Ge80 has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying 02+ intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV γ ray, and suggested it as evidence for shape coexistence in Ge80. We used the β decay from the 3- 22.4-keV state in Ga80 to enhance the population of low-spin states in Ge80, including any excited 0+ level, and γγ coincidences to investigate it. We observed a 1764-keV γ ray in coincidence with strong transitions in Ge80, thus not feeding the proposed 639-keV 02+. No connecting transitions from previously known levels to the 639-keV and 2403-keV 23+ states could be established either. Shell-model calculations for Ge isotopes and N=48 isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a 02+ state below ≈1200 keV in Ge80. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying 02+ state in Ge80. ; This work was supported by Spanish national projects FPA2015-65035-P, RTI2018-098868-B-I00, and PID2019- 104390GB-I00, by Grupo de Física Nuclear (GFN) at Universidad Complutense (Spain), by the U.S. DoE Grant No. DE-FG02-94ER40834, and by the German BMBF Grant 05P19PKFNA. The support by the European Union Seventh Framework through ENSAR (Contract No. 262010) and by the ISOLDE Collaboration and technical teams is acknowledged. ; Peer reviewed

11 pags., 10 figs., 5 tabs.-- Open Access funded by Creative Commons Atribution Licence 4.0 ; The structure of Si34 was studied through γ spectroscopy separately in the β- decays of Mg34 and Al34 at the ISOLDE facility of CERN. Different configurations in Si34 were populated independently from the two recently identified β-decaying states in Al34 having spin-parity assignments Jπ=4- dominated by the normal configuration π(d5/2)-1 - ν(f7/2) and Jπ=1+ by the intruder configuration π(d5/2)-1 - ν(d3/2)-1(f7/2)2. The paper reports on spectroscopic properties of Si34 such as an extended level scheme, spin and parity assignments based on log(ft) values and γ-ray branching ratios, absolute β feeding intensities, and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of Si34. Large scale shell-model calculations using the SDPF-U-MIX interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of SDPF-U-MIX, the N=20 shell gap, the level of mixing between normal and intruder configurations for the 01+, 02+, and 21+ states, and the absence of triaxial deformation in Si34. ; This work was partially supported by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS-UEFISCDI project number PN-II-RU-TE- 2014-4-1455, by the Romanian IFA Grant CERN/ISOLDE, by Research Foundation Flanders (FWO-Belgium), by GOA/2015/010 (BOF KU Leuven), and by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12). Support from the U.K. Science and Technology Facilities Council, the European Union Seventh Framework through ENSAR (Contract No. 262010), the MINECO (Spain) grants FPA2017-87568-P, FPA2015-64969-P, FPA2014-57196, FPA2015-65035-P, Programme "Centros de Excelencia Severo Ochoa" SEV-2016- 0597, the MEYS project SPIRAL2-CZ,EF16-013/0001679, the National Research, Development and Innovation Fund of Hungary via Project No. K128947, the European Regional Development Fund (Contract No. GINOP-2.3.3-15-2016- 00034), the German BMBF under contract 05P18PKCIA (ISOLDE), and "Verbundprojekt 05P2018" is also acknowledged. I.K. was supported by the National Research, Development and Innovation Office of Hungary (NKFIH), Contract No. PD 124717. ; Peer Reviewed