No abstract

We have observed that the positrons associated with a narrow peak in the positron spectrum from U + Th collisions are correlated with the simultaneous emission of electrons whose energy spectrum also contains a narrow peak. The mean energies and widths of the two peaks are equal within measurement errors. Neither the coincidence-peak intensity nor the energy distributions of the positrons and electrons can be accounted for by known nuclear internal-conversion processes. Similar observations have also been made in the Th + Th and Th + Cm collision systems.