Dr Brett Manning
PhD Thesis, Rutgers University (October 2014)
Atomic nuclei with a few nucleons beyond shell closures are important in understanding the evolution of single-particle structure, which is critical to the benchmarking of nuclear models. With radioactive ion beams, studies near the double closed shell nucleus 132Sn have been made possible. While the single-neutron states in 133Sn with N = 83 and 131Sn with N = 81 have recently been verified to be highly pure, it is important to study further from the N = 82 neutron shell closure.
Level energies and spectroscopic information for neutron-rich nuclei also provide important input for the rapid neutron capture r-process nucleosynthesis calculations. Specifically, it is important to know the location and strength of single-neutron states with orbital angular momentum L=1 when calculating neutron-capture rates. Surman and collaborators have performed sensitivity studies to show that varying neutron-capture rates can significantly alter final r-process abundances. However, there are many nuclei important to the r-process that cannot be studied. Extending studies to more neutron-rich nuclei will help constrain the nuclear shell model in extrapolating to nuclei even further from stability.
The (d,p) neutron transfer reaction has been measured in inverse kinematics with radioactive ion beams of 126Sn and 128Sn and a stable beam of 124Sn, all in inverse-kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory, utilizing the SuperORRUBA (Oak Ridge Rutgers University Barrel Array) of silicon detectors. The present work is combined with previous studies to complete the set of (d; p) studies on even mass tin isotopes from doubly-magic 132Sn to stable 124Sn and the systematics of L=1 and L=3 strengths. The results of the (d,p) study are used to map the fragmentation of single-neutron strengths in N ~ 82 tin isotopes and to calculate the direct-semidirect neutron capture on these even mass tin isotopes that are important for the astrophysical r-process.
