Analysis of the α-Particle Spectra from the ¹⁴³Nd(n_th,γα)¹⁴⁰Ce and ¹²³Te(n_th,γα)¹²⁰Sn Reactions

Abstract

The (n,γα) reaction, observed for the first time ten years ago¹⁾, offers an unique possibility to study γ transitions between highly excited states. Whereas the principal features of this two-step process are well known, i.e. the dependence of the α-particle spectrum both on the γ population Γ ^ℓ_γ γ (E_γ) ρ (I^π, E_ex) of the intermediate states and on their α-decay probability Γ ^ℓα_α (E_α), there still remain open questions about the structure of the involved states and the speed of the γ transitions. Until now hindrance factors for either E1 or M1 γ transitions could be deduced^2,3) under the extreme assumption that only one type of them contributes to the (n,γα) reaction.