Decay studies of K isomers in 254No

A detailed γ spectroscopic decay study of two K isomers in 254No was performed. In addition to the previously reported γ lines two new transitions of E=778, 856keV could be attributed to the decay pattern of 254m1No (T1/2=275±7 ms). The population of an excited band built up on this isomer (Kπ =8-) by the decay of 254m2No (T1/2=198±13 μs) could be proven by measuring delayed γ-γ coincidences between transitions stemming from the decay of both isomeric states. The energies of the band members could be established up to Iπ = 15-. A spontaneous fission branch of (2.0±1.2) x 10-4 was measured for 254m1No, an upper limit of ≤1.2 x 10-4 was estimated for 254m2No. These values demonstrate the high stability of multi-quasiparticle configurations against spontaneous fission. Evidence for an α decay branch of 254m1No in the order of 1 x 10-4 was found. (orig.)