  The ground state correlation energies associated with collective surface and
pairing vibrations are calculated for Pb- and Ca-isotopes. It is shown that
this contribution, when added to those predicted by one of the most accurate
modern nuclear mass formula (HFBCS MSk7 mass formula), reduces the associated
rms error by an important factor, making mean field theory, once its time
dependence is taken into account, a quantitative predictive tool for nuclear
masses.
