The $\beta$ decay of five heavy, neutron-rich nuclei, ${}^{203,204}$Pt and ${}^{200-202}$Ir, has been investigated following relativistic cold fragmentation reactions of lead projectiles using the FRS+RISING setup at GSI. This paper reports on the study of the low-lying states in the decay daughter nuclei ${}^{203,204}$Au and ${}^{200-202}$Pt. The characteristic $\gamma$ rays for each nucleus have been determined using $\beta$-delayed $\gamma$-ray spectroscopy. Tentative level schemes, relative intensities, and apparent $\beta$ feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total $\beta$ strength from high-energy first-forbidden $\beta$-decay transitions in this mass region.

• Received 9 April 2013

DOI:https://doi.org/10.1103/PhysRevC.88.014319