Quasi-exact expansion of the electron momentum density of the Hooke's   atom
  An analytic expansion of the exact one-electron momentum density of the Hooke's atom is derived for the case k = 1/4. Electron correlation is shown to have opposite effects on the momentum density, compared with the Moshinsky's atom, but is qualitatively similar to classical two-electron atomic systems at large momenta. 
S. Ragot