Integral cross section of isomeric state formation in (neutron,nucleon) reactions using an Am-Be source

The present work targeted the study of the isomeric state formation in (n,n') and (n,p) reactions using the spectral emission of an Am-241-Be neutron source which favors the (neutron, nucleon) reactions over the (n, gamma) and (n,2n) ones. The integral cross section of the isomeric nuclear states in the neutron-induced nucleon-emission reactions of fast neutrons on In-115, Hg-199, Ni-58, and Pt-195 was measured experimentally. The monitor reaction of neutrons was the In-115(n,n') In-115(m) using the evaluated integral cross section of 269(-1.5)(+13) mb, which was confirmed to have a constant isomeric ratio in the energy range between similar to 1.6 MeV and similar to 10 MeV. Integral cross sections for the Hg-199(n,n') Hg-199, Ni-58(n,p) Co-58(m), Ni-58(n,p) Co-58(m+g) and Pt-195(n,n') Pt-195(m) reactions were found to be 449 +/- 13 mb, 112 +/- 34 mb, 343 +/- 72 mb and 740 +/- 55 mb, respectively. Each experimental value was based on independent measurements of samples irradiated with a constant neutron flux from an Am-241-Be source (having standard emission probability). The experimental results are compared with the integrated cross sections from a new evaluation for neutron induced reactions weighted to standard neutron emission probability distribution. Integral values estimated from theoretical calculations and evaluated libraries were used for the examination of our results. Results confirmed that formation of isomeric states is sensitive to the neutron energy distribution. The behavior of the isomeric ratio of neutron reaction leading to isomeric state formation was found to be useful in order to distinguish between reactions suitable for use as monitor ones (yielding a constant isomeric ratio throughout the emission energy range) and those used to probe the disturbance in the neutron spectral distribution.