NEUTRON-INDUCED FISSION CROSS SECTION OF AM242M

The neutron-induced fission cross section of Am242m has been measured from 0.02 eV to 6 MeV by the time-of-flight method at the Livermore 30-MeV linear electron accelerator. The data are normalized at 0.0253 eV to a value of 6600 b measured in a reactor thermal-neutron flux. The cross section at 0.2 eV is 4700 b; at 1 eV it is 540 b; and at 4 MeV it is 2.1 b. The data are analyzed to obtain values for the neutron strength function Γn0D of 1.4×10-4, the level spacing D=1.2 eV, and the quantity 2πΓfD=2.5. All three quantities are quoted per spin state. The high cross section at low energies can be attributed to the unusually high value for 2πΓfD, and to the existence of a very large resonance at 0.173 eV. The fission cross section of Am241 also was measured in the MeV region and found to be 1.96±0.2 b at 2.5 MeV. © 1968 The American Physical Society.