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Cross-shell excitations inSi31

  • Author(s): Tai, P-L
  • Tabor, SL
  • Lubna, RS
  • Kravvaris, K
  • Bender, PC
  • Tripathi, Vandana
  • Volya, A
  • Carpenter, MP
  • Janssens, RVF
  • Lauritsen, T
  • McCutchan, EA
  • Zhu, S
  • Clark, RM
  • Fallon, P
  • Paschalis, S
  • Petri, M
  • Macchiavelli, AO
  • Reviol, W
  • Sarantites, DG
  • et al.
Abstract

© 2017 American Physical Society. The Si31 nucleus was produced through the O18(O18, αn) fusion-evaporation reaction at Elab=24MeV. Evaporated α particles from the reaction were detected and identified in the Microball detector array for channel selection. Multiple γ-ray coincidence events were detected in Gammasphere. The energy and angle information for the α particles was used to determine the Si31 recoil kinematics on an event-by-event basis for a more accurate Doppler correction. A total of 22 new states and 52 new γ transitions were observed, including 14 from states above the neutron separation energy. The positive-parity states predicted by the shell-model calculations in the sd model space agree well with experiment. The negative-parity states were compared with shell-model calculations in the psdpf model space with some variations in the N=20 shell gap. The best agreement was found with a shell gap intermediate between that originally used for A≈20 nuclei and that previously adapted for P32,34. This variation suggests the need for a more universal cross-shell interaction.

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