  Employing a recently-developed dispersive optical model (DOM) which allows a
complete description of experimental data both above (up to 200 MeV) and below
the Fermi energy in $^{40}$Ca, we demonstrate that elastic nucleon-nucleus
scattering data constrain the spectral strength in the continuum of orbits that
are nominally bound in the independent-particle model. In the energy domain
between 0 and 200 MeV, the integrated strength or depletion number is highly
sensitive to the separation of the IPM orbit to the scattering continuum. This
sensitivity is determined by the influence of the surface-absorption properties
of the DOM self-energy. For an ab initio calculation employing the self-energy
of the charge-dependent Bonn (CDBonn) interaction which only includes the
effect of short-range correlations, no such sensitivity is obtained and a
depletion of 4% is predicted between 0 and 200 MeV irrespective of the orbit.
The ab initio spectral strength generated with the CDBonn interaction
approaches the empirical DOM spectral strength at 200 MeV. Both spectral
distributions allow for an additional 3-5% of the strength at even higher
energies which is associated with the influence of short-range correlations. We
suggest that the non-local form of the DOM allows for an analysis of
elastic-nucleon-scattering data that directly determines the depletion of bound
orbits. While obviously relevant for the analysis of elastic nucleon scattering
on stable targets, this conclusion holds equally well for experiments involving
rare isotopes in inverse kinematics as well as experiments with electrons on
atoms or molecules.
