Suchergebnisse

12 pags., 16 figs., 4 tabs. ; We report the first detection of the second-forbidden, nonunique, 2+ → 0+, ground-state transition in the β decay of 20F. A low-energy, mass-separated 20F+ beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plasticscintillator detector. The β-decay branching ratio inferred from the measurement is bβ = [0.41 ± 0.08(stat) ± 0.07(sys)] × 10−5 corresponding to log f t = 10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on 20Ne is now known to within better than 25% at the relevant temperatures and densities ; This work has been supported by the Academy of Finland under the Finnish Centre of Excellence Programme (Nuclear and Accelerator Based Physics Research at JYFL 2012-2017) and Academy of Finland Grants No. 275389, No. 284516, No. 295207, and No. 312544. D.F.S. and G.M.-P. acknowledge the support of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)-Projektnummer 279384907-SFB 1245 "Nuclei: From Fundamental Interactions to Structure and Stars"; and the ChETEC COST action (CA16117), funded by COST (European Cooperation in Science and Technology). This project has been partly supported by the Spanish Ministry MINECO through the grant FPA2015-64969-P and has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 654002 (ENSAR2). O.S.K. acknowledges support from the Villum Foundation through Project No. 10117. P.C.S. acknowledges the support from the Faculty Initiation Grant (FIG) provided by IIT Roorkee. A.K. and M.H. acknowledge the support from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 771036 (ERC CoG MAIDEN). B.A.B. acknowledges the support from NSF Grant PHY-1811855.

6 pages, 2 figures.-- PACS nrs.: 24.30.Cz, 25.70.Gh.-- Presented at the Zakopane Conference on Nuclear Physics (Zakopane, Poland, Sep. 4–10, 2006). ; The Advanced Time Delayed method has been used to measure the lifetimes of excited states in the exotic nuclei Sb-134, Sb-135 and Te-136 populated in the beta decay of Sb-134, Sb-135 and Te-136, respectively. High purity Sn beams were extracted at the ISOLDE separator using a novel production technique utilizing the molecular SnS+ beams to isolate Sn from contaminating other fission products. Among the new results we have identified the 1/2+ state in Sb-135 and its E2 transition to the lower-lying 5/2+ state was found to be surprisingly collective. This measurement represents also one of the first applications of the LaBr3 scintillator to ultra fast timing. ; This work was supported by the NSF PHY04-57120, NSF PHY-0555366, Swedish Research Council, BMBF grant 06KY205I, the Alexander von Humboldt Foundation (WBW), the European Union Sixth Framework through RII3-EURONS (contract no. 506065) and the EU-RTD project TARGISOL (HPRI-CT-2001-50033). ; 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.