Auto-ionization of positrons in heavy ion collisions

Abstract

Autoionization of positrons occurs as a fundamentally new process of quantum electrodynamics, if empty 1s- or 2p _1/2− etc. electronic shells obtain binding energies larger than 2m _e c ². This effect should be experimentally observable in the scattering of very heavy ions (Z≧80) on each other since in such collisions superheavy electronic molecules are formed (superheavy quasi-molecules). The scattering mechanism and the distribution of autoionization positrons are discussed. The adiabaticity of the heavy ion collision is studied and the electron-positron pair production background to the ionization problem is estimated. Analytic solutions are obtained for 1/r-potentials for the caseZα≧1. The phase shifts of negative energy solutions in the case of cutoff Coulomb potentials reveal the accuracy of the autoionization formalism.