Scattering phase shift
= Scattering phase shift
{title2=$\delta_l$}
For elastic scattering by a real central potential, the phase shift $\delta_l(k)$ measures the phase difference between the asymptotic radial wave in angular-momentum channel $l$ and the corresponding free wave. Its channel <Partial-wave S-matrix> is $S_l=e^{2i\delta_l}$.
The phase shift parametrizes elastic <partial-wave scattering>, rather than general scattering phenomena.