RUI: collective excitations and shell structure in neutron-rich nuclei

The National Science Foundation Division of Physics awarded Ursinus College $150,000 on August 15, 2026, under the Mathematical and Physical Sciences program (CFDA 47.049) to support undergraduate research in experimental nuclear structure physics through August 31, 2029.

Ursinus College undergraduates will conduct experimental nuclear structure research in collaboration with the Facility for Rare Isotope Beams (FRIB) and Florida State University (FSU). The research program encompasses two experimental components. First, the group will measure Coulomb excitation of Ni-76 and conduct inverse-kinematics proton scattering measurements of Ni-74 and Ni-76 at FRIB to examine neutron and proton contributions to excitations of first excited states in neutron-rich nickel isotopes approaching doubly-magic Ni-78. Second, (D,T) and (D,He-3) pickup reactions will probe neutron- and proton-hole states. In parallel, the Ursinus group will develop and maintain detector simulations for the GRETA gamma-ray tracking array used across FRIB experiments and for the CEBRA scintillator detector array deployed with the Super Enge Split-Pole Spectrograph at FSU.

Undergraduate participants will gain practical skills in data acquisition, analysis, and detector simulation; explore AI coding tools; observe accelerator facility operations; and present findings at the Ursinus College Summer Fellows Symposium and at American Physical Society Division of Nuclear Physics meetings.

Place of performance is Collegeville, Pennsylvania.

Abstract

This award supports the engagement of ursinus college undergraduates in experimental nuclear structure research. The project is part of an ongoing collaboration with colleagues at the facility for rare isotope beams (frib) and florida state university (FSU). The ursinus college nuclear structure group will contribute to the understanding of the systematic evolution of single-particle and collective excitations through experimental work at frib and FSU. The group will also support the nuclear structure community through the continuing development of simulations of the greta gamma-RAY tracking array used in a wide range of experiments at frib and of the cebra array of cerium bromide scintillator detectors used with the super enge split-pole spectrograph (SE-SPS) at FSU. The project will contribute to the training of the stem workforce by maintaining an active research program in nuclear structure on the ursinus college campus. Undergraduate participants will apply their knowledge of physics outside the classroom, gain practical skills in data acquisition, analysis, and detector simulation, explore the use of AI coding tools, observe and participate in the operation of nuclear accelerator facilities and present their work at the ursinus college summer fellows symposium and at american physical society/division of nuclear physics meetings. The project is comprised of two independent experimental programs and the detector simulation efforts supporting each of them. First, the group will expand the empirical picture of the relative neutron and proton contributions to excitations of the first excited states of even-even neutron rich nickel isotopes approaching doubly-magic NI-78 with a coulomb excitation measurement of NI-76 and inverse-kinematics proton scattering measurements of NI-74 and NI-76 at frib. Second, the (d, t) and (d, he-3) pickup reactions will be used to study neutron- and proton-hole states in the FP shell using the SE-SPS. This will reveal how robust the n = 28 and z = 20 shell closures are. Specifically, measured angular distributions of outgoing t and he-3 particles will enable the identification of angular-momentum transfers and, thereby, the orbitals from which neutrons or protons were removed. Complementary (d, t gamma) and (d, he-3 gamma) experiments will also be carried out with the cebra+SE-SPS setup to study the gamma decay of the states populated in these reactions. The predicted alignment created in these light-ION transfer reactions will be tested through the measurement of particle-gamma angular correlations. Finally, the group will contribute to the nuclear science community by maintaining and improving simulations of greta and cebra. These and similar simulation codes are central tools for experimental design and for extracting experimental results from raw data. 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.- subawards are not planned for this award.