The calculation and derivation of microscopic optical potentials for calculating scattering observables for elastic scattering from spin-zero nuclei has a long tradition. So-called microscopic `full-folding' models based on a nuclear density matrix and a fully-off-shell two nucleon t-matrix have been developed mainly for closed shell nuclei heavier than Oxygen-16 in the 1990s. With the advent of ab initio structure calculations in the No-Core-Shell Model (NCSM) for light nuclei, and the symmetry-adapted (SA) NCSM for heavier nuclei, nonlocal as well as translationally invariant one-body densities can be constructed and employed in calculations of effective interactions in proton-nucleus scattering.

This talk will explain the approach based on the spectator expansion to proton-nucleus scattering and show how the first order term can be obtained consistently based on a given chiral nucleon-nucleon interaction. Results for proton and neutron scattering from ⁶He to ⁴⁰Ca in the energy regime between 65 and 200 MeV laboratory projectile energy will be shown with emphasis on recent work of proton and neutron scattering from ²⁴Mg to ³²Mg, where we show that ab initio calculations may give guidance to extrapolations of phenomenological optical potentials away from the valley of stability.

I will also discuss some current work based on SVD decomposition of off-shell NCSM one-body density matrices and leading order optical potentials derived from them.