Investigating high-j single-particle energies in Z = 51 nuclei

Abstract

The work of this thesis consists of a systematic study of low-lying, proton single- particle states in Z = 51 isotopes. States in 113-125Sb were populated via (alpha,t) and (3He,d) single-proton adding reactions, performed on stable even tin isotopes. The Yale tandem accelerator delivered beams of 37.5-MeV alpha particles and 25-MeV 3He nuclei for the reactions. Outgoing tritons and deuterons were momentum analysed using an Enge split-pole spectrometer. To obtain absolute cross sections, the product of target thickness and spectrometer aperture size was calibrated for each target, using sub-Coulomb alpha- particle elastic scattering. States were observed up to ∼4 MeV excitation energy. Angular momentum transfer assignments were made through comparison of angular distributions and ratios of cross sections between different reactions. Relative spectroscopic factors ex- tracted through a DWBA analysis allowed energy centroids of the observed single-particle strength to be reconstructed.These measurements build upon the results of a previous (alpha,t) study, which was per- formed on the same targets. The previous measurements estimated that ∼ 90% of the pieg7/2 and pieh11/2 strength was held in the lowest-lying 7/2+ and 11/2- states, respectively. The difference in energy of these states increased with increasing neutron excess, and al- though they were in agreement with theoretical calculations that included contributions of the tensor interaction, poor statistics limited the information obtained regarding the weak fragments of high-j single-particle strength. Careful examination of these fragments, with the use of greater statistics, has been performed in this work. The (3He,d) measurements aid in making l transfer assignments and provide complementary information regarding the low-j states.Binding energies of the pieg7/2 and pieh11/2 orbitals measured in this work were compared to the energies of the lowest-lying 7/2+ and 11/2- states and theoretical calculations that include the tensor interaction. Though shifted higher in energy due to the fragmentation, trends in the centroids appear to be consistent with the lowest-lying states. The trend of the pieg7/2-pieh11/2 energy difference is in quantitative agreement with the predicted effects of the tensor interaction, with increasing neutron excess.

Date of Award	31 Dec 2012
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Sean Freeman (Supervisor)