We report on a new, crystalline host-guest system for single molecule spectroscopy; dibenzanthanthrene (DBATT) in a naphthalene crystal. As compared to DBATT in an n-hexadecane Shpol’skii matrix (a combination studied earlier), this system is shifted to the red (618.7 nm), has a lower triplet yield and shorter triplet lifetimes. Thanks to the narrow lines of this system (20 MHz), to its high photostability and to the absence of spectral diffusion, even in strained crystals, we could measure line shapes and widths with great accuracy. As an illustration of the potential of this new system for quantum optical experiments, we present pump-probe experiments with strong laser fields. The experiments are in very good agreement with calculations based on Bloch’s equations, demonstrating the validity of these equations for single molecules in solids under intense resonant fields.