  We present the momentum distributions of the nucleus and of the electrons
from double ionization of the helium atom by Compton scattering of photons with
$h\nu=40$ keV. We find that the doubly charged ion momentum distribution is
very close to the Compton profile of the nucleus in the ground state of the
helium atom, and the momentum distribution of the singly charged ion to give a
precise image of the electron Compton profile. To reproduce these results,
non-relativistic calculations require the use of highly correlated initial- and
final-state wavefunctions.
