Collective structures in the odd-Ztransitional nuclei115,117I and121,123Sb

Collective properties of odd-Z ${}_{}{}^{115}{}_{}{}^{}$,117I and ${}_{}{}^{121}{}_{}{}^{}$,123Sb nuclei have been investigated via ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ ${(}^{12}$C,p2n${)}^{115}$I, ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ ${(}^{14}$N,2pn${)}^{117}$I, ${}_{}{}^{112}{}_{}{}^{}\mathrm{Sn}$ ${(}^{12}$C,αp2n${)}^{117}$I, and ${}_{}{}^{120}{}_{}{}^{}$,122Sn${(}^7$Li,α2n) ${}_{}{}^{121}{}_{}{}^{}$,123Sb reactions, using in-beam γ excitation, γ-γ coincidence, γ-W(θ) and pulsed-beam-γ measurements. The two collective features common to the Z>50 transition region were observed; the first, the occurrence of ΔJ=1 bands built on low-lying ${\mathrm{}(9/2)\mathrm{}}^{+}$ states, was found in all four nuclei, and the second, ΔJ=2 bands built on ${\mathrm{}(11/2)\mathrm{}}^{\mathrm{-}}$ states, was seen in ${}_{}{}^{115}{}_{}{}^{}$,117I. The ${\mathrm{}(9/2)\mathrm{}}^{+}$ and ${\mathrm{}(11/2)\mathrm{}}^{\mathrm{-}}$ band heads involve a 1$g_{9/2}$ proton hole and a 1$h_{11/2}$ quasiproton, respectively. The systematics of these band structures in the Z>50 transition region, which have been extended in this study, are presented and discussed in terms of collective interpretations.