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

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

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