Lifetimes in At211 and their implications for the nuclear structure above Pb208

Lifetimes of excited states in $^{211}\mathrm{At}$ were measured using the electronic $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ fast timing technique. The nucleus of interest was populated in a $^{208}\mathrm{Pb}(^{6}\mathrm{Li},3n)^{211}\mathrm{At}$ fusion-evaporation reaction at the FN Tandem accelerator of the Institute for Nuclear Physics, University of Cologne. The lifetimes of the $17/{2}_{1}^{\ensuremath{-}}$ and $23/{2}_{1}^{\ensuremath{-}}$ states were determined, together with an upper limit for the $13/{2}_{1}^{\ensuremath{-}}$ state. The experimental results are compared to two shell-model calculations, one using a semiempirical interaction for three particles in a single $j=9/2$ shell and the other using the modified Kuo-Herling interaction in a multi-$j$ model space.