Particle-core coupling in S 37

R. Chapman et al. ; 8 págs.; 6 figs.; 2 tabs.Excited states of the neutron-rich N=21 S37 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. The level scheme of S37 was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11/2-) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1f7/2 neutron to the first 2+ state of the S36 core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed. ©2016 American Physical SocietyWe would like to thank the technical staff of the INFN Legnaro National Laboratory for their support during this experiment. This work was supported by the EPSRC (U.K). Four of us (A.H,M.B, K.L.K., and A.P.) would like to acknowledge the receipt of financial support from EPSRC during the course of this work. A.J. would like to acknowledge support from the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5-4-P. Z.D. acknowledges financial support from OTKA Grant No. K100835.Peer Reviewe

First in-beam γ -ray study of the level structure of neutron-rich S 39

The neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2-). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ω shell-model calculations presented here. © 2016 American Physical Society

First in-beam γ -ray study of the level structure of neutron-rich S 39

R. Chapman et al. ; 8 págs.; 6 figs.; 1 tab.The neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2-). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ω shell-model calculations presented here. ©2016 American Physical SocietyThis work was supported in part by the EPSRC (UK) and by the European Union under Contract No. RII3-CT- 2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.) acknowledge financial support from the EPSRC. Z.M.W. acknowledges support from ORSAS and from the University of the West of Scotland. A.N.D. acknowledges support from the STFC. A.J. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación under Contracts No. FPA2007-66069 and No. FPA2009-13377-C02-02. Zs.D. acknowledges financial support from OTKA under Project No. K100835. S.S. acknowledges support from the Croatian Science Foundation under Project No. 7194. The contribution of the accelerator and target-fabrication staff at the INFN Legnaro National Laboratory is gratefully acknowledged.Peer Reviewe

Particle-core coupling in S 37

Excited states of the neutron-rich N=21 S37 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. The level scheme of S37 was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11/2-) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1f7/2 neutron to the first 2+ state of the S36 core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed. © 2016 American Physical Society

γ-ray spectroscopy of the A=23, T=1/2 nuclei 23Na and 23Mg: High-spin states, mirror symmetry, and applications to nuclear astrophysical reaction rates

Background: Obtaining reaction rates for nuclear astrophysics applications is often limited by the availability of radioactive beams. Indirect techniques to establish reaction rates often rely heavily on the properties of excited states inferred from mirror symmetry arguments. Mirror energy differences can depend sensitively on nuclear structure effects. Purpose: The present work sets out to establish a detailed comparison of mirror symmetry in the A=23, T=1/2 mirror nuclei 23Na and 23Mg both to high spin, and high excitation energy, including beyond the proton threshold. These data can be used to benchmark state-of-the-art shell-model calculations of these nuclei. Methods: Excited states in 23Na and 23Mg were populated using the 12C(12C,p) and 12C(12C,n) reactions at beam energies of 16 and 22 MeV, and their resulting γ decay was measured with Gammasphere. Results: Level schemes for 23Na and 23Mg have been considerably extended; highly excited structures have been found in 23Na, as well as their counterparts in 23Mg for previously known rotational structures in 23Na. Mirror symmetry has been investigated up to an excitation energy of 8 MeV and spin-parity of 13/2+. Excited states in the region above the proton threshold have been studied in both nuclei. Conclusions: A detailed exploration of mirror symmetry has been performed which heavily constrains expectations as to how mirror energy differences should evolve for different structures. Agreement with shell-model calculations provides confidence in using such estimations where real data are absent

First in-beam γ -ray study of the level structure of neutron-rich S 39

International audienceThe neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2−). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2− states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ℏω shell-model calculations presented here

Intruder negative-parity states of neutron-rich Si33

Yrast states in the neutron-rich 1433Si19 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. An experimental setup that combines the large-acceptance magnetic spectrometer PRISMA and the high-efficiency γ-ray detection array CLARA was used in the experiment. Four new γ-ray photopeaks at energies of 971, 1724, 1772, and 2655 keV were observed and assigned to the Si33 level scheme. The experimental level scheme is compared with the results of 1ω p-sd-pf large-scale shell-model calculations using the recently developed PSDPFB effective interaction; good agreement is obtained. The structure of the populated states of Si33 is discussed within the context of an odd neutron coupled to states of the Si32 core. © 2010 The American Physical Society.This work was supported in part by the EPSRC (UK) and by the European Union under Contract No. RII3-CT-2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.)acknowledge financial support from the EPSRC. Z.M.W acknowledges support from ORSAS and from the University of the West of Scotland. A.J. acknowledges financial supportfrom the Spanish Ministerio de Ciencia e Innovación under Contract Nos. FPA2007-66069 and FPA2009-13377-C02-02. Zs.D. acknowledges the financial support from OTKA Project No. K68801.Peer Reviewe