  Since effective potentials derived from Feynman diagrams are naturally given
in momentum space, we formulate the non-relativistic Coulomb problem entirely
in momentum representation. We give momentum wave functions for all quantum
numbers in one-dimensional integrals, even though they can be evaluated.
Angular momentum decomposed Green's functions are then compactly represented.
We apply this formalism to investigate the next to next leading order charm
effects on 1S bottomonium level shift. Our one insertion results are given
completely in analytic form and numerically agree with previous results. Our
two insertion results are also in agreement. The net effect of finite charm
mass is to decrease the bottom mass by 33 MeV, as determined through the
measured 1S energy.
