The β decay of the neutron-rich nuclides, 40-s ${}_{}{}^{139}{}_{}{}^{}\mathrm{Xe}$, 1.7-s ${}_{}{}^{141}{}_{}{}^{}\mathrm{Xe}$, and 0.4-s ${}_{}{}^{143}{}_{}{}^{}\mathrm{Xe}$ to levels of odd-Z ${}_{}{}^{139}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$, respectively, has been studied using sources isolated from fission products by on-line mass separation. The data collected include gamma-ray and conversion electron singles spectra as well as gamma-ray coincidence and angular correlation spectra. New levels have been identified in ${}_{}{}^{139}{}_{}{}^{}\mathrm{Cs}$ including a doublet at 393 keV, and new spin and parity assignments are proposed. New data are presented for ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$ levels in support of an earlier proposed level scheme by Talbert and Cook. Evidence for a 0.4-s half-life for ${}_{}{}^{143}{}_{}{}^{}\mathrm{Xe}$ has been found, and a level at 90 keV is proposed for ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$. The resulting level structures for the neutron-rich Cs nuclides are compared with level structures of other odd-Z neutron-rich nuclides and neutron deficient Cs nuclides. The transition from the structure observed near the closed N=82 neutron shell to deformed structures described by Nilsson model orbitals is discussed.

• Received 22 December 1987

DOI:https://doi.org/10.1103/PhysRevC.38.905