Discovery of the Origin of the Enormous Zr88 Neutron-Capture Cross Section and Quantifying Its Impact on Applications

The probability per unit area for a radioactive ^{88}Zr nucleus (83.4 d half life) to absorb neutrons across resonance energies-its neutron-capture resonance integral-is the largest ever reported [Shusterman et al.,Phys. Rev. C 103, 024614 (2021).PRVCAN2469-998510.1103/PhysRevC.103.024614] and implies that the neutron-capture cross section is orders of magnitude larger than previously thought at energies relevant to nuclear test diagnostics and nucleosynthesis applications such as the νr process [Xiong et al.,Phys. Rev. Lett. 132, 192701 (2024).PRLTAO0031-900710.1103/PhysRevLett.132.192701]. However, these applications require the shape of this cross section across a range of energies, not just this integral quantity. We measured the ^{88}Zr neutron total cross section from 0.0253 to 500 eV. Because the same resonances or other nuclear structure responsible for the neutron-capture cross section are reflected in the total cross section, we used these data to extract the former from the latter as a function of energy. Our data reveal a resonance at 0.171 eV and result in a thermal neutron-capture cross section of 771 000±31 000 b, in good agreement with the recently published value. In contrast, the neutron-capture resonance integral extracted from our data is 15 210±670 b and is roughly a factor of 200 smaller than the recently reported value. We discuss the impact of this difference on applications.