  We give here the proof that pair creation in a time dependent potentials is
possible. It happens with probability one if the potential changes
adiabatically in time and becomes overcritical, that is when an eigenvalue
enters the upper spectral continuum. The potential may be assumed to be zero at
large negative and positive times. The rigorous treatment of this effect has
been lacking since the pioneering work of Beck, Steinwedel and Suessmann in
1963 and Gershtein and Zeldovich in 1970.
