  Based on the quantum interference between two-identical-nucleus scattering at
energies around the Coulomb barrier, the barrier positions for
$^{58}$Ni+$^{58}$Ni and $^{16}$O+$^{16}$O are extracted from Mott oscillations
in the angular distributions around 90$^{\circ}$ for the first time. The angle
separation of pairs of Mott scattering valleys around 90$^{\circ}$ has a direct
relationship with the closest distance between two nuclei in elastic
scattering. Together with the barrier height from fusion excitation function,
the extracted barrier position provides a sensitive probe to constrain the
model predictions for the nucleus-nucleus potential barrier.
