  The observed features of $\psi'$ to $J/\psi$ suppression in $pA$ and
nucleus-nucleus collisions can be explained in terms of a two-component
absorption model. For the hard component of the absorption due to the
interaction of the produced $c\bar c$ systems with baryons at high relative
energies, the absorption cross sections are insensitive to the radii of the
$c\bar c$ systems, as described by the Additive Quark Model. For the soft
component due to the low energy $c \bar c$ interactions with soft particles
produced by other baryon-baryon collisions, the absorption cross sections are
greater for $\psi'$ than for $J/\psi$, because the breakup threshold for
$\psi'$ is much smaller than for $\psi$.
