2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/217104The many-particle spectrum of an isotropic frequency gap medium doped with impurity resonance atoms is studied using the Bethe ansatz technique. The spectrum is shown to contain pairs of quantum correlated ``gap excitations'' and their heavy bound complexes (``gap solitons''), enabling the propagation of quantum information within the classically forbidden gap. In addition, multiparticle localization of the radiation and the medium polarization occurs when such a gap soliton is pinned to the impurity atom.8 pages, RevTEX, to appear in Phys. Rev. LettQuantum PhysicsCondensed Mattertext