Samples of ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ were obtained by on-line mass-separation techniques applied to ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ thermal-fission products. Half-lives of (6.9±0.1) and (2.5±0.1) min have been measured for the ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sn}$ beta decays. Decay schemes are proposed based on gamma-ray energies and intensities and gamma-gamma coincidence results. A new half-life of (17.7±0.1) min, besides the well known 4.4 h one, was observed in the ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ decay. A level scheme fed by this decay is proposed taking into account our results and previously reported nuclear reactions data. The ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ structure is compared with a particle-core coupling calculation.

RADIOACTIVITY ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ decays [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n_{\mathrm{th}}, f)$]; on-line measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coincidences, $T_{\frac{1}{2}}$, Ge(Li) detectors; ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Te}$ deduced levels. Mass-separated ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Sb}$ activities.

• Received 11 August 1981

DOI:https://doi.org/10.1103/PhysRevC.26.621