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

The structure of 208Po resulting from the EC/β + decay of 208At was studied at CERN's ISOLDE Decay Station (IDS). The high statistics afforded by the high yield of 208At and the high efficiency HPGe clusters at the IDS allowed for greater insight into lower intensity transitions and thus significant expansion of the 208Po level scheme. Furthermore, investigation into the isomeric state yielded a new half life 377(9) ns in addition to uncovering new transitions populating the state. ; The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 654002. As well as the Science and Technology Facilities Council (UK) through grants ST/P005314/1, ST/L005743/1, ST/J000051/1, ST/L005670/1, and ST/P004598/1 and (PHR) by the UK Department of Business, Energy and Industrial Strategy (BEIS) via the National Measurement System. Further funding was provided by the German BMBF under contract 05P18PKCIA and "Verbundprojekt 05P2018" as well as the Spanish MINECO grant FPA2015-65035-P. ; Peer reviewed

13 pags., 5 figs., 2 tabs. ; The structure of Po208 populated through the EC/β+ decay of At208 is investigated using γ-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed γ rays which have been (re)assigned a position. The level scheme is compared to shell model calculations. Through this analysis approximately half of the β-decay strength of At208 is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations. This mass region provides an excellent testing ground for the competition between allowed and first-forbidden β-decay calculations, important for the detailed understanding of the nucleosynthesis of heavy elements. ; The research leading to these results received funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 654002. Support from the European Union Seventh Framework through ENSAR Contract No. 262010, as well as the Science and Technology Facilities Council (U.K.) through Grants No. ST/P005314/1, No. ST/L005743/1, No. ST/J000051/1, No. ST/L005670/1, and No. ST/P004598/1, the German BMBF under Contract No. 05P18PKCIA and "Verbundprojekt 05P2018" as well as Spanish MINECO Grants No. FPA2015-65035- P and No. FPA2017-87568-P, FWO Vlaanderen (Belgium), GOA/2015/010 (BOF KU Leuven), the Excellence of Science Programme (EOS-FWO), the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12), the Polish National Science Centre under Contracts No. UMO-2015/18/M/ST2/00523 and No. UMO-2019/33/N/ST2/03023, National Science Foundation (U.S.) Grant No. PHY1811855, and the Romanian IFA project CERN-RO/ISOLDE is acknowledged. P.H.R. acknowledges support from the U.K. Department for Business, Energy and Industrial Strategy via the National Measurement Office ; Peer reviewed