Non-hydrogenic wavefunctions in momentum space

Quantum defect theory is applied to the calculation of non-hydrogenic radial wavefunctions in the momentum space representation, given in the form of Hankel transform integrals of the position space functions in the Coulomb approximation. It is shown that, even for low excited states, the momentum space functions for important values of the momentum are insensitive to the inner-core region of the atom. Analytical expressions are presented and illustrative examples are given for some Rydberg states in sodium, magnesium and caesium.