One-neutron transfer study of Xe-137 and systematics of 13/2(1)(+) and 13/2(2)(+) levels in N=83 nuclei

Excited states in Xe-137 have been studied by using the near-barrier single-neutron transfer reactions C-13(Xe-136, C-12 gamma) Xe-137 and Be-9(Xe-136, Be-8 gamma) Xe-137 in inverse kinematics. Particle-gamma and particle-gamma gamma coincidence measurements have been performed with the Phoswich Wall and Digital Gammasphere detector arrays. Evidence is found for a 13/2(2)(+) level (E = 3137 keV) and for additional high-lying 3/2(-) and 5/2(-) states. The results are discussed in the framework of realistic shell-model calculations. These calculations are also extended to the 13/2(1)(+) and 13/2(2)(+) levels in the N = 83 isotonic chain. They indicate that there is a need for a value of the neutron 0i(13/2) single-particle energy (E-SPE = 2366 keV) lower than the one proposed in the literature. It is also demonstrated that the population patterns of the j = l +/- 1/2 single-particle states in Xe-137 are different for the two targets used in these measurements and the implications of this effect are addressed.