Structure of Mg 30 explored via in-beam γ -ray spectroscopy

N. Kitamura, K. Wimmer, N. Shimizu, V. M. Bader, C. Bancroft, D. Barofsky, T. Baugher, D. Bazin, J. S. Berryman, V. Bildstein, A. Gade, N. Imai, T. Kröll, C. Langer, J. Lloyd, E. Lunderberg, G. Perdikakis, F. Recchia, T. Redpath, S. SaenzD. Smalley, S. R. Stroberg, J. A. Tostevin, N. Tsunoda, Y. Utsuno, D. Weisshaar, A. Westerberg

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Background: In the "island of inversion,"ground states of neutron-rich sd-shell nuclei exhibit strong admixtures of intruder configurations from the fp shell. The nucleus Mg30, located at the boundary of the island of inversion, serves as a cornerstone to track the structural evolution as one approaches this region. Purpose: Spin-parity assignments for excited states in Mg30, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of Mg30 was investigated by in-beam γ-ray spectroscopy mainly focusing on firm spin-parity determinations. Method: High-intensity rare-isotope beams of Mg31, Mg32, Si34, and P35 bombarded a Be target to induce nucleon removal reactions populating states in Mg30. γ rays were detected by the state-of-the-art γ-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multinucleon removal reactions from different projectiles were exploited to gain complementary information. Results: With the aid of the parallel momentum distributions, an updated level scheme with revised spin-parity assignments was constructed. Spectroscopic factors associated with each state were also deduced. Conclusions: Results were confronted with large-scale shell-model calculations using two different effective interactions, showing excellent agreement with the present level scheme. However, a marked difference in the spectroscopic factors indicates that the full delineation of the transition into the island of inversion remains a challenge for theoretical models.

Original languageEnglish
Article number054318
JournalPhysical Review C
Issue number5
StatePublished - Nov 12 2020


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