Compound nucleus
= Compound nucleus
An intermediate excited <atomic nucleus> formed when the reactants' available <energy> is redistributed among nuclear degrees of freedom before decay. Its resolved levels can appear as resonances. An isolated level's formation and decay into particular channels are described by <partial decay widths> in the <Breit-Wigner resonance cross section>; direct reactions and overlapping resonances need not obey that simple one-level description.