Neutron-Induced Fission Cross Section ofAm242m

The neutron-induced fission cross section of ${\mathrm{Am}}^{242m}$ 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 $〈\frac{{\Gamma }_{n^0}}{D}〉$ of 1.4×${10}^{-4\mathrm{}}$, the level spacing $D=1.2\mathrm{}$ eV, and the quantity $2\pi 〈\frac{{\Gamma }_f}{D}〉=2.5\mathrm{}$. All three quantities are quoted per spin state. The high cross section at low energies can be attributed to the unusually high value for $2\pi 〈\frac{{\Gamma }_f}{D}〉$, and to the existence of a very large resonance at 0.173 eV. The fission cross section of ${\mathrm{Am}}^{241}$ also was measured in the MeV region and found to be 1.96±0.2 b at 2.5 MeV.