Reinhardt, J; Müller, U; Müller, B; Greiner, W, *The decay of the vacuum in the field of superheavy nuclear systems*, vol. 303 no. 3
(1981),
pp. 173-188 [doi] .
**Abstract:**

*In the strong Coulomb field of a nucleus or quasimolecule with Z≳172 a change of the QED vacuum has been predicted, signalled by the spontaneous emission of positrons if holes in the K-shell are available. The dynamical semiclassical theory of positron excitation in heavy ion scattering is presented and extended to collisions with nuclear contact. Interference patterns in the energy spectrum of the emitted positrons and, for sufficiently long reaction time T, the emerging of a characteristic line at the position of the 1 sσ-resonance is predicted. The position and width of the 1 sσ-resonance is calculated in dependence on the nuclear configuration, the effect of electron screening is taken into account. Recent experimental indications [1, 2] for structures in the spectra of positrons emitted in U-U collisions at energies close to the Coulomb barrier are discussed in terms of spontaneous positron creation. The observed spectra could be explained under the assumption of long lasting nuclear reactions (T≳4·10-20 s) with a cross section in the millibarn region. Various consequences of this interpretation are discussed. © 1981 Springer-Verlag.*