  Motivated by recent Raman and resonant inelastic X-ray scattering experiments
performed for Mott insulators, which suggest formation of excitons in these
systems, we present a theory of exciton formation in the upper Hubbard band.
The analysis based on the spin polaron approach is performed in the framework
of an effective t-J model for the subspace of states with one doubly occupied
site. Our results confirm the existence of excitons and bear qualitative
resemblance to experimental data despite some simplifications in our approach.
They prove that the basic underlying mechanismof exciton formation is the same
as that which gives rise to binding of holes in weakly doped antiferromagnets.
