Quantum reflection and dwell times of metastable states

The concept of phase and dwell times used in tunneling is extended to quantum collisions to derive a relation between the phase and dwell time delays in scattering. This relation can be used to remove the near threshold s-wave singularities in the Wigner-Eisenbud delay times and amounts to an extension of the concept of quantum reflection to strong interactions. Dwell time delay emerges as the quantity which gives the correct behaviour of the density of states of a metastable state at all energies. This fact is demonstrated by investigating some recently found metastable states of mesic-nuclei.