Atomic dark matter

We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Protohalo formation can be suppressed below Mₚᵣₒₜₒ ~ 10³ - 10⁶ M_ for weak scale dark matter due to Ion-Radiation interactions in the dark sector. Moreover, weak-scale dark atoms can accommodate hyperfine splittings of order 100, consistent with the inelastic dark matter interpretation of the DAMA data while naturally evading direct detection bounds.