  Collective bremsstrahlung of vector meson fields in relativistic nuclear
collisions is studied within the time-dependent Walecka model. Mutual
deceleration of the colliding nuclei is described by introducing the effective
stopping time and average rapidity loss of baryons. It is shown that
electromagnetic decays of virtual omega-mesons produced by bremsstrahlung
mechanism can provide a substantial contribution to the soft dilepton yield at
the SPS bombarding energies. In particular, it may be responsible for the
dilepton enhancement observed in 160 AGev central Pb+Au collisions. Suggestions
for future experiments to estimate the relative contribution of the collective
mechanism are given.
