Suchergebnisse

6 pags., 4 figs., 1 tab. ; The β decay of Hg208 into the one-proton hole, one neutron-particle Tl81208127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Qβ window, only three negative parity states are populated directly in the β decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden β decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing 0+→0-β decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators. ; This work was supported by the European Union under Contracts No. 262010 (ENSAR) and No. 654002 (ENSAR2), the Science and Technology Facilities Council (UK), the German BMBF under Contract No. 05P18PKCIA and "Verbundprojekt 05P2018," the MINECO Projects No. FPA2015-65035-P, No. RTI2018- 098868-B-I00, No. FPA2015-64969-P, and No. FPA2017- 87568-P (Spain), 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 Romanian IFA project CERN-RO/ISOLDE and the Polish National Science Centre under Contracts No. UMO-2015/18/M/ST2/00523 and No. UMO-2019/33/N/ST2/03023. P. H. R. and S. M. J. acknowledge support from the UK Department for Business, Energy and Industrial Strategy via the National Measurement Office. Zs. P. acknowledges support from the ExtreMe Matter Institute EMMI at the GSI Helmholtzzentrum fr Schwerionenforschung, Darmstadt, German

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

12 pags., 5 figs., 3 tabs. ; The β decay of Hg207 into the single-proton-hole nucleus Tl207 has been studied through γ-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the πs1/2-1, πd3/2-1, and πh11/2-1 shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states (s1/2-coupled) are identified and three more states (d3/2-coupled) are tentatively assigned using spin-parity inferences, while further h11/2-coupled states may also have been observed for the first time. Comparisons are made with state-of-the-art large-scale shell model calculations and previous observations made in this region, and systematic underestimation of the energy of the octupole vibrational states is noted. We suggest that in order to resolve the difference in predicted energies for collective and noncollective t=1 states (t is the number of nucleons breaking the Pb208 core), the effect of t=2 mixing may be reduced for octupole-coupled states. The inclusion of mixing with t=0,2,3 excitations is necessary to replicate all t=1 state energies accurately. ; 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. Support from the European Union Seventh Framework through ENSAR Contract No. 262010, the Science and Technology Facilities Council (UK), the MINECO Projects No. FPA2015-64969-P and No. FPA2017-87568-P (Spain), FWOVlaanderen (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 German BMBF under Contract No. 05P18PKCIA + "Verbundprojekt 05P2018," the Polish National Science Centre under Contracts No. UMO-2015/18/M/ST2/00523 and No. UMO-2019/33/N/ST2/03023, the National Science Foundation (US) Grant No. PHY-1811855 and the Romanian IFA project CERN-RO/ISOLDE is acknowledged. P.H.R. and S.M.J. acknowledge support from the UK Department for Business, Energy and Industrial Strategy via the National Measurement Office.

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