1. Structure of Mg30 explored via in-beam γ -ray spectroscopy
- Author
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T. Kröll, Naofumi Tsunoda, D. Weisshaar, Thomas Redpath, C. Bancroft, F. Recchia, A. Westerberg, S. Saenz, Christoph Langer, Kathrin Wimmer, Eric Lunderberg, N. Kitamura, Noritaka Shimizu, S.R. Stroberg, D. Smalley, T.R. Baugher, J. S. Berryman, Y. Utsuno, D. Barofsky, J. Lloyd, N. Imai, V. M. Bader, Alexandra Gade, J. A. Tostevin, V. Bildstein, G. Perdikakis, and D. Bazin
- Subjects
Physics ,010308 nuclear & particles physics ,Island of inversion ,Nuclear structure ,01 natural sciences ,Momentum ,Excited state ,0103 physical sciences ,Gamma spectroscopy ,Atomic physics ,010306 general physics ,Nucleon ,Spectroscopy ,Beam (structure) - Abstract
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 $^{30}$Mg, 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 $^{30}$Mg, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of $^{30}$Mg was investigated by in-beam $\gamma$-ray spectroscopy mainly focusing on firm spin-parity determinations. Method: High-intensity rare-isotope beams of $^{31}$Mg, $^{32}$Mg, $^{34}$Si, and $^{35}$P bombarded a Be target to induce nucleon removal reactions populating states in $^{30}$Mg. $\gamma$ rays were detected by the state-of-the-art $\gamma$-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multi-nucleon 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.
- Published
- 2020