A spectroscopic investigation of high-spin states in ${}_{}{}^{201,203}{}_{}{}^{}\mathrm{At}$ was performed by means of the reactions ${}_{}{}^{192,194}{}_{}{}^{}\mathrm{Pt}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$,5n)${}_{}{}^{201,203}{}_{}{}^{}\mathrm{At}$ with ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ energies between 85 and 100 MeV. In-beam measurements of $\gamma$-ray excitation functions, $\gamma -\gamma$ coincidences, $\gamma$-ray angular distributions, and pulsed-beam-$\gamma$ timing were made to determine the decay scheme, level energies, $\gamma$-ray multipolarities, spin-parity assignments, and isomeric lifetimes. The yrast and near-yrast level structures were established up to $J\sim \frac{25}{2}$, and several isomers with mean lifetimes around 20 ns were observed. The systematic trends of level energies of the odd-mass astatine ($Z=85\mathrm{}$) isotopes are discussed in terms of proton-particle configurations of ${}_{85}{}^{211}{}_{}{}^{}\mathrm{At}_{126}^{}{}_{}{}^{}$ coupled to neutron-hole configurations of the corresponding even-mass lead isotones.

NUCLEAR REACTIONS ${}_{}{}^{192,194}{}_{}{}^{}\mathrm{Pt}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$,5n), $E=85-100\mathrm{}$ MeV, measured $\gamma -\gamma$ coincidence, excitation functions, $\gamma$-ray angular distributions, pulsed-beam-$\gamma$ timing; deduced ${}_{}{}^{201,203}{}_{}{}^{}\mathrm{At}$ level energies, spins and parities, lifetimes, transition rates.

• Received 3 May 1983

DOI:https://doi.org/10.1103/PhysRevC.28.1171