Analogue resonances in odd isotopes of antimony

Abstract

Differential cross sections and analyzing powers were measured at several angles for protons incident on 124Sn and 122Sn at laboratory energies between 7.2 MeV and 12.0 MeV and on 120Sn between 9.6 MeV and 11.5 MeV. The resonances observed in this energy region correspond to states in 125Sn, 123Sn and 121Sn below 4 MeV excitation. The orbital angular momentum, resonance energy, full width and proton partial width of each resonance were extracted from the cross-section excitation functions. The total angular momentum of each resonance was determined from the analyzing-power excitation functions. The present assignments are in good agreement with the results of (d, p) experiments. Optical-model analyses of off-resonance angular distributions measured at several proton energies were used to determine parameters to characterize the off-resonance scattering. Spectroscopic factors were calculated using two approaches: R-matrix theory and the shell-model approach. The two calculations yielded comparable spectroscopic factors for the resonances at lower excitation energies, but the agreement was not as good for the high-lying resonances. Agreement with spectroscopic factors determined from (d, p) reactions is reasonable. Mixing phases calculated with the shell-model approach were in better agreement with experimental mixing phases than those determined with the R-matrix theory.