The structure of eta-nucleus bound systems (eta mesic nuclei) is investigated as one of the tools to study in-medium properties of theN(1535) (N*) resonance by using chiral models to incorporate the mediumeffects of the N* resonance.

We find that the shape and the depth of the eta-nucleus opticalpotential are strongly affected by the in-medium properties of the N*and nucleon. Especially, the existence of the repulsive core of theeta-nucleus potential at the nuclear center with an attractive part atthe nuclear surface is concluded in the chiral doublet model, while therepulsive core does not appear in the chiral unitary model prediction.

We calculate the level structure of eta bound states in these chiraloptical potentials and find that the level structure is sensitive tothe in-medium properties of the N*. The (d, 3He) spectra are alsoevaluated for the formation of these bound states for various kinds oftarget nuclei to investigate the experimental feasibility.