Müller, B; Rafelski, J; Greiner, W, *Electron wave functions in over-critical electrostatic potentials*,
Il Nuovo Cimento A Series 10, vol. 18 no. 3
(1973),
pp. 551-573 [doi] .
**Abstract:**

*The mathematical properties of the solutions of the Dirac equation in over-critical external potentials are investigated. The 1/r Coulomb potential is treated as the limit R → 0 of cut-off Coulomb potentials (R is the cut-off parameter). The results are interpreted in terms of quantum electrodynamics. A number of new physical phenomena occur in quantum electrodynamics of strong fields. One of the most interesting ones is the autoionization of positrons (energyless creation of electron-positron pairs) in over-critical external fields. © 1973 Società Italiana di Fisica.*