  We consider trasfer-ionization in collisions of fast (3.6 -- 11 MeV/u)
protons, alpha-particles and lithium nuclei with helium atoms. There are just a
few basic mechanisms contributing to this process which can be grouped into
correlated ones, which crucially depend on the electron-electron interaction,
and uncorrelated, which do not need this interaction to proceed. We show that
by exploring momentum spectra of the emitted electrons the correlated and
uncorrelated mechanisms can be cleary separated from each other. This
exploration also enables one to get insight into subtle details of the dynamics
of transfer-ionization.
