YIELD OF THE FISSIONING ISOMER IN THE REACTION AM-241(N,N')

The spontaneous fission of Am-241 in an isomeric state has been invest igated in a pulsed beam of neutrons from an electrostatic accelerator. The spontaneously fissioning isomer with half-life approximately 1.5 mus was excited by neutrons with mean energy 4.5 MeV, The fission frag ments were detected by means of the scintillation method. The relative probability of fission via the isomeric state, (1.4 +/- 0.3) . 10(-4) , and the half-life, 0.9 +/- 0.3 mus, have been measured. Analysis of the yields of fissioning isomers in the (n,n') and (n,gamma) reactions shows that the yield is systematically higher in the former case.