β decay ofRa228and possible level structures inAc228

An iron-free beta spectrometer with pre- and post-acceleration of electrons was used to study \ensuremath{\beta} branches and conversion electrons at very low energies in the \ensuremath{\beta} decay of $^{228}\mathrm{Ra}$. Results of conversion-electron and \ensuremath{\gamma}-ray spectroscopy are analyzed using \ensuremath{\beta} selection rules and two-quasiparticle-rotor model considerations. A tentative $^{228}\mathrm{Ac}$ level scheme, including model-dependent spin-parity and configuration assignments consistent with the available data, is presented.