Resonant Pair Production in Strong Electric Fields
The heavy ion-atom collision experiments at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, have revealed an intriguing and largely unexplained pattern of positron emission. With the combined atomic number of the colliding nuclei Zu=Z1+Z2 ranging between 165 and 188 and with projectile energies of ~6MeV/u (i.e. close to the Coulomb barrier), a set of narrow e+ lines were observed1–3 with c.m. kinetic energies ranging between 240 and 410 KeV and typical widths of 50–80 KeV. Even more remarkably, in one set of experiments4 the positrons of a narrow peak in the positron spectrum were seen to be correlated with the emission of electrons whose energy spectrum also contains a narrow peak of the same energy and width (within measurement errors). Three such e+e− structures were found at sum kinetic energies of 620, 760 and 810 KeV.
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