Nuclear Levels of Even Sn Isotopes Populated in the Decay of In Isomers

Abstract

The decay of the following neutron-rich indium isomers produced by 14-15-MeV neutron bombardments of isotopically enriched tin samples have been studied with beta and gamma scintillation techniques: 5.0±0.5-sec and 4.35±0.05-min ${\mathrm{In}}^{118}$, 3.2±0.4-sec and 44.3±1.5-sec ${\mathrm{In}}^{120}$, and 7.5±0.8 sec-${\mathrm{In}}^{122}$. The disintegration of the 3.5-min ${\mathrm{Sb}}^{118}$ isomer has been investigated by using a highly mass-separated ${\mathrm{Te}}^{118}$ source. Numerous levels in the corresponding tin isotopes were found to be populated, and the level schemes are compared with the theoretical calculations of Kisslinger and Sorensen and of Arvieu et al. The systematics of odd-odd In isomers is discussed in light of the spectroscopic data and the nuclear-shell model. The isomeric cross-section ratios of the ($n, p$) reaction forming the ${\mathrm{In}}^{116}$, ${\mathrm{In}}^{118}$, and ${\mathrm{In}}^{120}$ isomers were measured and are briefly discussed.