In-beam -spectroscopy of the transitional nucleus ^217Ac

High-spin states in the transitional ^217Ac nucleus are established up to 3. 8 MeV excitation energy and I^ = 41/2^+ with the addition of around 20 new transitions. The structure of the yrast and near-yrast states below the 29/2^+ isomer is revisited. The inconsistencies in the level schemes reported earlier are resolved. The level structure above the 29/2^+ isomer is established for the first time. Large-basis shell-model calculations with the KHPE interaction are performed to compare the experimentally observed level energies with the theoretical predictions. A comparison with the systematics of the N = 128 isotones suggests that the yrast structures result from a weak coupling of the odd proton to the even-even 216Ra core, which is consistent with the shell-model configurations. Furthermore, alpha decay of the 29/2^+ isomer is revisited and the decay scheme established from this work is discussed in the framework of the shell model.