Kind of the basic question of atomic physics is momentum distribution of single electron of ground state hydrogen atom - especially the power in its high-energy tail (HTMD: high-tail momentum distribution), which should have strong impact especially on various scattering experiments. Fock's 1935 non-relativistic quantum derivation leads to 1/p^6 tail. However, I have recently found a 2001 Eugene Oks paper with a long list of references claiming that experiments suggest "heavier tails": much lower power, like 1/p^4 or even lower: http://iopscience.iop.org/article/10.1088/0953-4075/34/11/315/pdf e.g. "The point we are trying to make is that the above fundamental dispute still remains unresolved: the experiments seem to favour a HTMD of ∼1/p^k , where k is at least 1.5 times smaller than in the quantum HTMD." So I wanted to ask which power should be used to describe the real ground state hydrogen atom?