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A method of spin assignment of neutron resonances based on capture gamma-ray detection

Nuclear Physics A
Publication Date
DOI: 10.1016/0375-9474(68)90833-6
  • Nuclear Reactions


Abstract In a time-of-flight neutron spectrometer, capture gamma rays were detected by two NaI(Tl) crystals. Single and coincidence counts were registered separately. It is shown that, with a proper choice of the energy threshold for single counts, the ratio of singles to coincidences in an s-wave resonance of a given nucleus is characteristic of the spin of the level. The interpretation of the experiment is supported by a numerical simulation of the gamma decay process. Experimental results are presented for odd-neutron target nuclei with spin I = 5 2 and I = 7 2 . Spins were assigned to 50 resonances in 105Pd, 36 resonances in 99Ru and 101Ru, 24 resonances in 95Mo and 97Mo and 46 resonances in 177Hf. Isotopic identification of resonances was performed in Pd and Ru. An indication of variation with spin of the s-wave neutron strength function in the direction S(I + 1 2 ) > S(I − 1 2 ) is found for 177Hf(n, γ). The comparison of the level densities of the two spin states gives a lower limit for the spin cut-off parameter σ min = 3.3 −0.1 +0.5 for the compound nucleus 106Pd and σ min = 3.1 −0.1 +0.5 for 178Hf.

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