We study few-body bound states of charged particles subject to attractive zero-range/short-range plus repulsive Coulomb interparticle forces. The characteristic length scales of the system at zero energy are set by the Coulomb length scale D and the Coulomb-modified effective range reff. We study shallow bound states of charged particles with D >> reff and show that these systems obey universal scaling laws different from neutral particles. An accurate description of these states requires both the Coulombmodified scattering length and the effective range unless the Coulomb interaction is very weak (D → ∞). Our findings are relevant for bound states whose spatial extent is significantly larger than the range of the attractive potential. These states enjoy universality – their character is independent of the shape of the short-range potential.

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Keywords: Universality; Bound states; Coulomb interaction