Cross-shell excitations in Si 31

P. L. Tai, S. L. Tabor, R. S. Lubna, K. Kravvaris, P. C. Bender, Vandana Tripathi, A. Volya, M. P. Carpenter, R. V.F. Janssens, T. Lauritsen, E. A. McCutchan, S. Zhu, R. M. Clark, P. Fallon, S. Paschalis, M. Petri, A. O. Macchiavelli, W. Reviol, D. G. Sarantites

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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.

Original languageEnglish
Article number014323
Number of pages12
JournalPhysical Review C
Issue number1
Publication statusPublished - 28 Jul 2017

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