Klauder's coherent states for the radial Coulomb problem in a uniformly   curved space and their flat-space limits
  First a set of coherent states a la Klauder is formally constructed for the Coulomb problem in a curved space of constant curvature. Then the flat-space limit is taken to reduce the set for the radial Coulomb problem to a set of hydrogen atom coherent states corresponding to both the discrete and the continuous portions of the spectrum for a fixed \ell sector. 
Myo Thaik and Akira Inomata