LEAPS-MPS: Experimental Nuclear Structure Studies

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This award will fund a research program in fundamental nuclear structure physics at South Carolina State University (SC State). The Principal Investigator and his group will investigate the structure of neutron-rich nuclei with mass numbers near 165 and so-called mirror nuclei with mass numbers near 70 that do not exist naturally in nature but can be produced at an accelerator facility. Understanding these nuclei is important for advancing knowledge of the process by which nucleons (protons and neutrons) organize into nuclei and what patterns (prolate, oblate or triaxial) emerge from those organizations. The project enhances understanding of these basic questions by accelerating nuclei to high energies or angular momentum and measuring gamma- and beta-particle radiation that is emitted when they interact with other atomic nuclei. Experiments will be performed using state-of-the-art instruments and accelerator facilities in the United States. The research activities will involve SC State University undergraduate students; the student population there is 93% African American and 55% female. Participation in this research will prepare and motivate minority students to continue their studies to graduate school or enter the workforce in STEM fields. These students will not only advance their professional skill set and become better scientists, but they will also be exposed to diverse areas such as national nuclear facilities, government laboratories, and medical diagnostic and treatment facilities. A central goal of the project is to build an active research program in nuclear structure at SC State. The research supported by this award will help to gain insights into the properties of nuclei by establishing and studying their basic modes of excitation i.e. gamma and beta-decays. Experiments will be performed using the Argonne Tandem Linac Accelerator System (ATLAS) and Californium Rare Isotope Breeder Upgrade (CARIBU) radioactive beam facilities at Argonne National Laboratory. Gamma-rays will be detected using one of the most powerful detectors in the world (Gammasphere). Neutron-rich nuclei in the mass region A ~ 165 are of special interest for the study of nuclear structure because of the rapid onset of deformation between 88 and 90 neutrons. The observation of detailed changes in nuclear structures within this mass region continues to provide insights into the nuclear force. The isospin symmetry breaking in the A ~ 70 mirror nuclei is another subject of interest in this study. It will also help to describe very important nuclear properties. Investigations following gamma- and beta-decays, aided by potential energy surface and shell-model calculations, are helpful to the analysis of the effects of the nuclear force governing nuclear shapes and the resulting sequence of single-particle orbitals. The structure of deformed, neutron-rich nuclei in the rare-earth region is also of significant interest for the field of astrophysics. Although much progress is being made in our understanding of the r-process, a satisfactory explanation for the elemental peak in abundance near A = 165 is still elusive. The quest to understand the origin of this peak may be key to correctly identifying the astrophysical conditions for the r-process. In order to address these issues, additional experiments are needed. The proposed project will explore deformed structures and other nuclear properties of the A ~ 70 and 165 nuclei.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.