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 ²⁴¹Am-Be neutron source which favors the (neutron, nucleon) reactions over the (n, γ) and (n,2n) ones. The integral cross section of the isomeric nuclear states in the neutron-induced nucleon-emission reactions of fast neutrons on ¹¹⁵In, ¹⁹⁹Hg, ⁵⁸Ni, and ¹⁹⁵Pt was measured experimentally. The monitor reaction of neutrons was the ¹¹⁵In(n,n^')^115mIn using the evaluated integral cross section of 269_-15⁺¹³ mb, which was confirmed to have a constant isomeric ratio in the energy range between ∼1.6 MeV and ∼10 MeV. Integral cross sections for the ¹⁹⁹Hg(n,n^')^199mHg, ⁵⁸Ni(n,p)^58mCo, ⁵⁸Ni(n,p)^58m+gCo and ¹⁹⁵Pt(n,n^')^195mPt 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 ²⁴¹Am-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.