The high-spin states in the odd-mass ${}_{}{}^{127-133}{}_{}{}^{}\mathrm{Cs}$ have been investigated using the ${}_{}{}^{120-124}{}_{}{}^{}\mathrm{Sn}$(${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$,$3n$) ${}_{}{}^{127-131}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$($\alpha$,$2n$)${}_{}{}^{129}{}_{}{}^{}\mathrm{Cs}$ and ${}_{}{}^{126-130}{}_{}{}^{}\mathrm{Te}$(${}_{}{}^6{}_{}{}^{}\mathrm{Li}$,$3n$)${}_{}{}^{129-133}{}_{}{}^{}\mathrm{Cs}$ reactions, to study the collective properties of these Cs isotopes. In-beam measurements of $\gamma$-ray excitations, $\gamma -\gamma$ coincidences, $\gamma$-ray angular distributions, and pulsed-beam—$\gamma$ timing were performed with Ge(Li) detectors to establish the level schemes. Two collective features have been observed in these odd-mass ${}_{}{}^{127-133}{}_{}{}^{}\mathrm{Cs}$ nuclei: $\Delta J=2\mathrm{}$ bands built on the $\frac{11}{2^{-}}$($1h_{\frac{11}{2}}$ quasi-proton) states and on the $\frac{7}{2^{+}}$ ($1g_{\frac{7}{2}}$ quasiproton) states. The systematics of these band structures in ${}_{}{}^{127-133}{}_{}{}^{}\mathrm{Cs}$, as well as in ${}_{}{}^{119-125}{}_{}{}^{}\mathrm{Cs}$, are presented and discussed in terms of the particle-plus-rotor and particle-plus-vibrator models.

NUCLEAR REACTIONS ${}_{}{}^{120-124}{}_{}{}^{}\mathrm{Sn}$(${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$,$3n$)${}_{}{}^{127-131}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{T}$($\alpha$,$2n$)${}_{}{}^{129}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{126-130}{}_{}{}^{}\mathrm{Te}$(${}_{}{}^6{}_{}{}^{}\mathrm{Li}$,$3n$)${}_{}{}^{129-133}{}_{}{}^{}\mathrm{Cs}$; measured $\gamma -\gamma$ coincidences, $\gamma (E,\theta ,t)$; deduced level schemes in odd-mass ${}_{}{}^{127-133}{}_{}{}^{}\mathrm{Cs}$, $\gamma$ multipolarities, $J^{\pi }$. Enriched targets, Ge(Li) detectors. NUCLEAR STRUCTURE Odd-mass ${}_{}{}^{127-133}{}_{}{}^{}\mathrm{Cs}$, calculated $\frac{11}{2^{-}}$ $\Delta J=2\mathrm{}$ rotational bands.

• Received 2 August 1978

DOI:https://doi.org/10.1103/PhysRevC.19.207