  The connection of the binding energy and width of possible bound eta-mesic
states is given to the complex scattering length for s-states in the hope that,
with knowledge of the final state interaction this could be useful in searches
of these states. In spite of the strong direct potential dependence of both
observables this connection is seen to be very model independent even for
various nuclei once the influence of also the effective range is considered.
The importance of this term is pointed also for data analyses. Although the
nucleus considered here is 12C, extension to other nuclei is implied in the
background work.
