Experiments on Search and Investigation of Unusual Neutron Resonances

Abstract

The measurements of neutron capture and scattering for ²³⁸U have been performed in order to search and investigate neutron resonances with unusual properties. Resonance widths have been determined. For 721 eV resonance from capture data an anomalously low value of radiation width of Г_δ=3.2±0.5 meV was obtained, which qualitatively conforms with the result from [1] and is indicative of pronounce of this resonance. It appears from scattering data that Г_δ for this resonance seems to be larger than the mentioned value. Г_δ amounts to 23±3 meV for 1211 eV resonance which similar to 721 eV resonance has a large fission width. This value coincides with the ²³⁸U average radiation width within measurement errors and is significantly larger than that of 6.6 meV calculated in [1]. At the same time the results of capture δ-quanta spectrum measurement showed that this spectrum for both resonances mentioned is the same within errors and is not different from that for other resonances. The results obtained indicate that there is no reason to assert that 721 and 1211 eV resonances are associated with the states of the second well of fission barrier [1]. Probably, they correspond to unusual states of various nature.