120Sn(p,α)117In and 121Sb(p,α)118Sn reactions: identification of the 117In and 118Sn homologous states

To investigate the spectator role of the d(5/2) unpaired proton outside the Z=50 closed shell, the 120Sn(p,α)117In and 121Sb(p,α)118Sn reactions have been measured in high resolution experiments, performed with the 23 MeV proton beam of the Munich MP Tandem, using the Stern-Gerlach type polarized hydrogen ion source and the Q3D magnetic spectrograph. The homologous states arise from the coupling of the d(5/2) unpaired proton with the configuration excited in 117In. In this paper we present the results concerning the 118Sn levels homologous of the 117In(9/2+) G.S. and 1/2- 0.315 MeV parent states. We have identified many levels of 118Sn homologous and more than the sextet of positive parity states expected, from 2+ to 7+ by the weak coupling model, pointing out the presence of an important fragmentation of the parent 117In 9/2+ G.S. strength. The cumulative cross-section of these daughter states of 118Sn accounts for 82% of the cross-section associated with the population of the parent state