Induced Decay of the Neutral Vaccum in Overcritical Fields Occurring in Heavy-Ion Collisions

In critical or nearly critical heavy-ion collisions, induced as well as spontaneous energyless $e^{-}{e}^{+}$ pair creation result in the decay of the neutral vacuum. Induced transitions from the negative-energy continuum into a vacant molecular $1s$ level can occur even in the absence of diving and produce a substantial enhancement and broadening of the previously considered spontaneous positron spectrum. Total cross sections of 5 b have been calculated for U-U collisions.