 Nuclear resonance

A nuclear resonance is an enhanced nuclear reaction or scattering response near the energy of an accessible quasi-bound nuclear state. For an isolated resonance, a common energy dependence is ${\sigma }_{ab}(E)\propto {\Gamma }_a{\Gamma }_b/[(E-E_r{)}^2+(\Gamma /2{)}^2]$, where $E_r$ is the resonance energy, $\Gamma$ the total width and ${\Gamma }_a,{\Gamma }_b$ partial widths for entrance and exit channels.

The lifetime scale is $\tau \sim \hslash /\Gamma$: narrower states persist longer. Spin factors, wavelength factors and interference with background amplitudes complete a cross-section model. Resonance spacings and widths provide input to statistical nuclear-reaction calculations.^[ref]