Resonance Absorption of Neutrons in Rhodium, Antimony, and Gold

The following experiments were performed on the resonance neutrons of Rh, Sb¹²¹, and Au: absorption in the element itself, absorption in boron, measurement of the total activation in an extended volume of hydrogenous material. The constants evaluated are the resonance energy Eᵣ, the absorption coefficient for self-indication Kᵣ, and the level width Γ. We found: for rhodium, Γ=0.16 ev; for antimony, Eᵣ=14 ev, Kᵣ=4 cm²/g, Γ=0.8 ev; for gold, Eᵣ=2.6 ev, Kᵣ=40 cm²/g, Γ=0.11 ev. In antimony and gold, the measurements indicate that a small fraction of the resonance activity induced in thin detectors is due to levels of higher energy. The observed absorption coefficient for thermal neutrons Kₜₕ in rhodium and gold is found to agree with the one calculated from the Breit and Wigner formula, by taking into account only the resonance level observed. In Sb, the calculated Kₜₕ is about six times larger than the one observed, which suggests the interference effect of negative levels.