We give a particle description of atom–field eigenstates in a three-dimensional spherical geometry of infinite volume by mapping the problem onto the anisotropic Kondo model. The spectrum has a rich bound state structure in comparison with models where the rotating wave approximation is made. It is shown how to obtain the Jaynes–Cummings model states in the limit of weak coupling. Nonperturbative Lamb shifts and decay rates are computed. The massive Kondo model is introduced to model light localization in the form of photon–atom bound states in photonic crystals.