Decay studies of K isomers in No-254

A detailed gamma spectroscopic decay study of two K isomers in No-254 was performed. In addition to the previously reported gamma lines two new transitions of E = 778, 856 keV could be attributed to the decay pattern of No-254m1 (T-1/2 = 275 +/- 7ms). The population of an excited band built up on this isomer (K-pi = 8(-)) by the decay of No-254m2 (T-1/2 = 198 +/- 13 mu s) could be proven by measuring delayed gamma-gamma coincidences between transitions stemming from the decay of both isomeric states. The energies of the band members could be established up to I-pi = 15(-). A spontaneous fission branch of (2.0 +/- 1.2) x 10(-4) was measured for No-254m1, an upper limit of <= 1.2 x 10(-4) was estimated for No-254m2. These values demonstrate the high stability of multi-quasiparticle configurations against spontaneous fission. Evidence for an alpha decay branch of No-254m1 in the order of 1 x 10(-4) was found.