γ, γγ-coincidence, internal conversion electron, and γ-ray angular distribution spectra of the ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$(p,nγ${)}^{118}$Sb reaction were measured at different bombarding proton energies between 5.5 and 7.5 MeV. γ, γγ-coincidence, and internal conversion electron spectra of the ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ (α,nγ${)}^{118}$Sb reaction were also measured at ${\mathit{E}}_{\mathrm{\alpha }}$=14.5 MeV. Ge(HP), Ge(Li), Ge(LEPS) γ-ray detectors, as well as a superconducting magnetic lens electron spectrometer [with Si(Li) detectors], were used in the experiments. About 210 (including ∼130 new) γ rays have been assigned to ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sb}$. The deduced ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sb}$ level scheme contains more than 70 new levels. On the basis of the internal conversion coefficients, Hauser-Feshbach analysis of (p,n) reaction cross sections, γ-ray angular distributions, and other arguments spin and parity values have been determined. The ‘‘parabolic rule’’ prediction of the energy splitting of different proton-neutron multiplets enabled the identification of many proton-neutron multiplet states. The energy spectrum and electromagnetic properties have been calculated in the framework of the interacting boson-fermion-fermion–odd-odd truncated quadrupole phonon model, and reasonably good agreement has been obtained between experimental and theoretical results.

• Received 17 March 1992

DOI:https://doi.org/10.1103/PhysRevC.46.1218