Trends in neutron single-particle energies below N=82

  • Alan Howard

Student thesis: Phd

Abstract

Two separate investigations are described, linked by their common interest in single-particle structure around the N=82 shell closure. A systematic study of single-particle strength below the N=82 shell closure is reported. States in 137Ba, 139Ce, 141Nd and 143Sm were populated using the single-neutron removal reactions (p,d) and (3He,alpha) at beam energies of 23 MeV and 34 MeV, respectively. Absolute cross sections are presented for all observed states. Relative spectroscopic factors have been determined through a dwba analysis. The observed g 7/2 strength is consistently lower than that of h11/2 across all four isotones. It is postulated that as much as 50% of the g7/2 strength is fragmented into unresolved states which form part of the reaction background below 3.5 MeV. A speculative analysis based upon the observed strength reveals a relative behaviour of the g7/2 and h11/2 centroid energies that is in qualitative agreement with the predicted action of the tensor force.Details are presented also from an exploratory study of the 132Sn region using the 136Xe + 238U reaction at 926 MeV. The time-of-flight spectrometer prisma was used to identify the beam-like reaction products, and a mass resolution > 1/200 and Z-resolution of ∼ 1/60 is reported. The total production yields at the focal plane are compared to calculations using the multi-nucleon transfer code grazing and rather poor agreement found for transfer of more then a few nucleons. The prospects for future studies in the region, particularly lifetime measurements, are discussed.
Date of Award31 Dec 2011
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorSean Freeman (Supervisor)

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