Electromagnetic decays of excited states in ^{261}Sg (Z=106) and ^{257}Rf (Z=104)

An isomeric one-quasineutron state, likely based on the [725]11/2(-) Nilsson level, was identified in (261)Sg by its decay via internal conversion electrons. The state has an excitation energy of approximate to 200 keV and a half-life of 9.0(-1.5)(+2.0) mu s. (261)Sg has the highest Z and A of any nucleus in which the electromagnetic decay of an isomeric state was observed to date. A separate experiment was performed on the a daughter nucleus of (261)Sg, namely (257)Rf. Spectroscopy of delayed gamma rays and converted electrons from (257)Rf resulted in the identification of a K isomer at an excitation energy of approximate to 1125 keV with a half-life of 134.9 +/- 7.7 mu s. The spin of the isomeric state is tentatively assigned I = 21/2, 23/2 and the state likely decays to a rotational band built on the [725]11/2(-) Nilsson level via a Delta K = 5 or 6 transition. The present results provide new information on excited states in the transactinide region, which is important for testing models of the heaviest elements.