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: Weak-scale dark atoms can accommodate hyperfine splittings of order 100 keV, consistent with the inelastic dark matter interpretation of the DAMA data while naturally evading direct detection bounds. Moreover, protohalo formation can be suppressed below M_proto ~ 10³-10⁶M_odot for weak scale dark matter due to Ion-Radiation and Ion-Atom interactions in the dark sector.