  This paper focused on showing that the fully differential cross section of
ionization during a collision of a proton and an antiproton with a hydrogen
atom is directly expressed by the time-dependent wave function. For the
projectile, wave function corresponding to the specific scattering angle was
converted by two-dimensional Fourier transform from the wave functions of
corresponding to impact parameters. This wave function shows how the ejected
electron probability density distribution varies with time. We are shown that
the calculation of the fully differential cross section of ionization can be
directly determined by the local value of the wave function without the need to
calculate the spatial integral for calculating the transition amplitude. It has
been shown that the direct determination of the fully differential cross
section by this time-dependent wave function is in good agreement with the
results of determined the traditional method is by the transition amplitude.
