Neutron cross sections for ¹⁵¹Eu below 1 eV

Total and activation cross-section measurements on ¹⁵¹Eu have been performed with monochromatic neutrons between 0.02 eV and 0.75 eV and with thermalized neutrons. The following results have been obtained: σ_nt(Eu) = 4590 ± 70 b at 0.0253 eV; σ_nγ(¹⁵¹Eu) = 9184 ± 140 b at 0.0253 eV; σ_act(¹⁵¹Eu(n,γ)^152mEu) = 3236 ± 120 b at 0.0253 eV and 2809 ± 120 b in a thermalized neutron spectrum T = 313 K) giving a Westcott g-factor = 0.87 ± 0.02; the resonance parameters of the bound level are: E_o = -3.61 ± 0.02 meV, Γ = 95.80 ± 0.01 meV, σ_o√|E_o| = 1696 ± 70 b · eV 1 2; the isomeric ratio R = σ_actσ_{n, γ} = 0.360 ± 0.02 for the bound level, 0.380 ± 0.035 for the 0.321 eV resonance and 0.270 ± 0.012 for the 0.460 eV resonance. The Westcott g(T) function, calculated with the present results agrees very well with experiment.