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We employ a collective vibration coupled-channel model to describe the nucleon-O16 cluster systems, obtaining low-excitation spectra for O17 and F17. Bound and resonance states of the compound systems have been deduced, showing good agreement with experimental spectra. Low-energy scattering cross sections of neutrons and protons from O16 also have been calculated and the results compare well with available experimental data.

One theoretical method for studying nuclear scattering and resonances is via the multichannel algebraic scattering (MCAS) formalism. Studies to date with this method have used a simple collective-rotor prescription to model target states with which a nucleon couples. While generally these target states all belong to the same rotational band, for certain systems it is necessary to include coupling to states outside of that main band. Here, we extend MCAS to allow coupling of different strengths between such states and the rotor band. This is an essential consideration in studying the example examined herein, the scattering of neutrons from $^{22}\mathrm{Ne}$.

The question of how the scattering cross section changes when the spectra of the colliding nuclei have low-excitation particle-emitting resonances is explored using a multi- channel algebraic scattering (MCAS) method. As a test case, the light-mass nuclear target 8 Be, being particle-unstable, has been considered. Nucleon-nucleus scattering cross sections, as well as the spectra of the compound nuclei formed, have been determined from calculations that do, and do not, consider particle emission widths of the target nuclear states. The resonant character of the unstable excited states introduces a problem because the low-energy tails of these resonances can intrude into the sub-threshold, bound-state region. This unphysical behaviour needs to be corrected by modifying, in an energy-dependent way, the shape of the target resonances from the usual Lorentzian one. The resonance function must smoothly reach zero at the elastic threshold. Ways of achieving this condition are explored in this paper.

A nucleon-nucleus interaction model has been applied to ascertain the underlying character of the negative-parity spectra of four isobars of mass-7, from neutron- to proton-emitter drip lines. With a single nuclear potential defined by a simple coupled-channel model, a multichannel algebraic scattering approach (MCAS) has been used to determine the bound and resonant spectra of the four nuclides, of which {sup 7}He and {sup 7}B are particle unstable. Incorporation of Pauli blocking into the model enables a description of all known spin-parity states of the mass-7 isobars. We have also obtained spectra of similar quality by using a large space no-core shell model. Additionally, we have studied {sup 7}Li and {sup 7}Be using a dicluster model. We have found a dicluster-model potential that can reproduce the lowest four states of the two nuclei, as well as the relevant low-energy elastic scattering cross sections. But, with this model, the rest of the energy spectra cannot be obtained.

Analyzing powers in low-energy neutron scattering from $^{12}\mathrm{C}$ are calculated in an algebraic momentum-space coupled-channel formalism, that is, a multichannel algebraic scattering (MCAS) theory. The results are compared with recently obtained experimental data. The channel-coupling potentials have been defined previously to reproduce the total cross section and subthreshold bound states of the compound system. Without further adjustment, good agreement with data for the analyzing powers is obtained.

Cross sections from low-energy neutron-nucleus scattering have been evaluated using a coupled channel theory of scattering. Both a coordinate-space and a momentum-space formalism of that coupled-channel theory are considered.A simple rotational model of the channel interaction potentials is used to find results using two relevant codes, ECIS97 and MCAS, so that they may be compared. The very same model is then used in the MCAS approach to quantify the changes that occur when allowance is made for effects of the Pauli principle., Comment: 6 pages, 3 figures