Reduction of spectroscopic overlap across the $Z=8$ shell in neutron-rich nuclei (2024)

Background: The recent discovery and spectroscopic measurements of ${}^{27}\mathrm{O}$ and ${}^{28}\mathrm{O}$ suggests the disappearance of the $N=20$ shell structure in these neutron-rich oxygen isotopes.

Purpose: We measured one- and two-proton removal cross sectionsfrom ${}^{27}\mathrm{F}$ and ${}^{29}\mathrm{Ne}$, respectively, extracting spectroscopic factors and comparing them to shell model overlap functions coupled with eikonal reaction model calculations.

Method: The invariant mass technique was used to reconstruct the two-body (${}^{24}\mathrm{O}+n$) and three-body (${}^{24}\mathrm{O}+2n$) decay energies from knockout reactions of ${}^{27}\mathrm{F}$ (106.2 MeV/u) and ${}^{29}\mathrm{Ne}$ (112.8 MeV/u) beams impinging on a ${}^9\mathrm{Be}$ target.

Results: The one-proton removal from ${}^{27}\mathrm{F}$ strongly populated the ground state of ${}^{26}\mathrm{O}$ and the extracted cross sectionof $3.4_{-1.5}^{+0.3}$ mb agrees with eikonal model calculations that are normalized by the shell model spectroscopic factors and account for the systematic reduction factor observed for single nucleon removal reactions within the models used. For the two-proton removal reaction from ${}^{29}\mathrm{Ne}$ an upper limit of 0.08 mb was extracted for populating states in ${}^{27}\mathrm{O}$ decaying though the ground state of ${}^{26}\mathrm{O}$.

Conclusions: The measured upper limit for the population of the ground state of ${}^{26}\mathrm{O}$ in the two-proton removal reaction from ${}^{29}\mathrm{Ne}$ indicates a significant difference in the underlying nuclear structure of ${}^{27}\mathrm{F}$ and ${}^{29}\mathrm{Ne}$.

• Received 9 March 2024
• Accepted 25 April 2024

DOI:https://doi.org/10.1103/PhysRevC.109.054325

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Nuclear Physics

T. Redpath^1,2,*, P. Guèye^1,3,†, T. Baumann¹, B. A. Brown¹, A. Cunningham^2,‡, P. A. DeYoung⁴, N. Frank⁵, C. R. Hoffman⁶, A. N. Kuchera⁷, B. Monteagudo Godoy⁴, C. Persch^4,§, A. Revel^1,3, W. F. Rogers⁸, M. Thoennessen^1,3, J. A. Tostevin⁹, and D. Votaw^1,3,∥

• ¹Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
• ²Department of Chemistry, Virginia State University, Petersburg, Virginia 23806, USA
• ³Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
• ⁴Department of Physics, Hope College, Holland, Michigan 49422-9000, USA
• ⁵Department of Physics, Engineering, and Astronomy, Augustana College, Rock Island, Illinois 61201, USA
• ⁶Physics Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
• ⁷Department of Physics, Davidson College, Davidson, North Carolina 28035, USA
• ⁸Department of Physics, Indiana Wesleyan University, Marion, Indiana 46953, USA
• ⁹Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom

• ^*tredpath@vsu.edu
• ^†gueye@frib.msu.edu
• ^‡Present address: Morehouse School of Medicine, Atlanta, GA 30310, USA.
• ^§Present address: Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309, USA.
• ^∥Present address: U.S. Department of Defense, Washington, DC 20301, USA.