In this paper we wish to report on the first observation of the beta decay of the very neutron-rich nucleus ${}_{}{}^{117}{}_{}{}^{}\mathrm{Rh}$. It was produced via 23 MeV proton induced fission of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ using the ion guide set-up of the LISOL separator. A beta half-life of 0.44±0.04 s was measured for this nucleus from the decay of the beta-coincident K x rays of Pd. The half-lives of neutron-rich Rh isotopes are compared with the newest model calculations. Three gamma rays of 34.6, 131.7, and 481.6 keV were found to be associated with the decay of ${}_{}{}^{117}{}_{}{}^{}\mathrm{Rh}$. Its proposed beta decay scheme and the decay of the recently discovered 19 ms isomer in ${}_{}{}^{117}{}_{}{}^{}\mathrm{Pd}$ imply spin and parity of 11/$2^{\mathrm{-}}$ for the isomer fed directly in fission.

• Received 1 July 1991

DOI:https://doi.org/10.1103/PhysRevC.44.R935