  The so called "barrier distribution" derived from quasi-elastic
backscattering of heavy ions gives us, in fact, an information about the
"reaction threshold distribution". For light nuclear systems these
distributions are quite close, but for heavy ones (when interaction of nuclei
becomes more and more complicated and the potential barrier can disappear at
all) they may significantly differ. The same should hold also for weakly bound
neutron rich projectiles, for which the neutron transfer and break-up reaction
channels play an important role at near-barrier energies. This is not a
terminology problem but important finding, because experiments on measurement
of the backward angle quasi-elastic scattering for deriving the "barrier
distributions" for heavy nuclear systems (which may be used for the production
of superheavy elements) are planned to be performed in several laboratories.
