57 research outputs found
Competition between Allowed and First-Forbidden β Decay: The Case of Hg 208 → Tl 208
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,
Germa
First -decay spectroscopy of and new -decay branches of
19 pags., 14 figs., 3 tabs.The decay of the neutron-rich and was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number above the shell. The -delayed -ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three -decay branches of were established, two of which were observed for the first time. Population of neutron-unbound states decaying via rays was identified in the two daughter nuclei of and , at excitation energies exceeding the neutron separation energy by 1 MeV. The -delayed one- and two-neutron emission branching ratios of were determined and compared with theoretical calculations. The -delayed one-neutron decay was observed to be dominant -decay branch of even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of . Transitions following the decay of are reported for the first time, including rays tentatively attributed to . In total, six new levels were identified in on the basis of the coincidences observed in the and decays. A transition that might be a candidate for deexciting the missing neutron single-particle state in was observed in both decays and its assignment is discussed. Experimental level schemes of and are compared with shell-model predictions. Using the fast timing technique, half-lives of the , and levels in were determined. From the lifetime of the state measured for the first time, an unexpectedly large transition strength was deduced, which is not reproduced by the shell-model calculations.M.P.-S. acknowledges the funding support from the Polish National Science Center under Grants No.
2019/33/N/ST2/03023 and No. 2020/36/T/ST2/00547 (Doctoral scholarship ETIUDA). J.B. acknowledges
support from the Universidad Complutense de Madrid under the Predoctoral Grant No. CT27/16-
CT28/16. This work was partially funded by the Polish National Science Center under Grants No.
2020/39/B/ST2/02346, No. 2015/18/E/ST2/00217, and No. 2015/18/M/ST2/00523, by the Spanish
government via Projects No. FPA2017-87568-P, No. RTI2018-098868-B-I00, No. PID2019-104390GB-I00,
and No. PID2019-104714GB-C21, by the U.K. Science and Technology Facilities Council (STFC), the German BMBF
under Contract No. 05P18PKCIA, by the Portuguese FCT under the Projects No. CERN/FIS-PAR/0005/2017, and
No. CERN/FIS-TEC/0003/2019, and by the Romanian IFA Grant CERN/ISOLDE. 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. M.Str. acknowledges the funding from the European Union’s Horizon 2020 research
and innovation program under Grant Agreement No. 771036 (ERC CoG MAIDEN). J.P. acknowledges support from the
Academy of Finland (Finland) with Grant No. 307685. Work at the University of York was supported under STFC Grants
No. ST/L005727/1 and No. ST/P003885/1
Investigation of the Δn = 0 selection rule in Gamow-Teller transitions : The β-decay of 207 Hg
Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn=0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N>82) and Z=82 (for N>126). The level of forbiddenness of the Δn=1ν1g 9/2 →π0g 7/2 transition has been investigated from the β − decay of the ground state of 207 Hg into the single-proton-hole nucleus 207 Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g 7/2 −1 state in 207 Tl, an upper limit of 3.9×10 −3 % was obtained for the probability of this decay, corresponding to logft>8.8 within a 95% confidence limit. This is the most stringent test of the Δn=0 selection rule to date
Isolation and Properties of a Metal-Dependent Endopeptidase from Human Uterus Hydrolysing Synthetic Collagenase Substrates
Exporting the British constitution: Responsible government in New Zealand, Canada, Australia and Ireland
The Effect of Whole- and Partial-body X-irradiation on the Metabolism of Collagen in Polyethylene Sponges and the Urinary Excretion of Pyrrole-2-carboxylic Acid
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