  Compound resonances in nucleon-nucleus scattering are related to the discrete
spectrum of the target. Such resonances can be studied in a unified and general
framework by a scattering model that uses sturmian expansions of postulated
multichannel interactions between the colliding nuclei. Associated with such
expanded multichannel interactions are algebraic multichannel scattering
matrices. The matrix structure of the inherent Green functions not only
facilitates extraction of the sub-threshold (compound nucleus) bound state
spin-parity values and energies but also readily gives the energies and widths
of resonances in the scattering regime. We exploited also the ability of the
sturmian-expansion method to deal with non-local interactions to take into
account the strong non-local effects introduced by the Pauli principle. As an
example, we have used the collective model (to second order) to define a
multichannel potential matrix for low energy neutron-C12 scattering allowing
coupling between the 0+ (ground), 2+ (4.4389 MeV), and 0+ (7.64 MeV) states.
The algebraic S matrix for this system has been evaluated and the sub-threshold
bound states as well as cross sections and polarizations as functions of energy
are predicted. The results are reflected in the actual measured data, and are
shown to be consistent with expectations as may be based upon a shell model
description of the target and of the compound nucleus.
