Positron emission in elastic collisions of fully ionized high-Z heavy ions

Recent theoretical investigations of pair-production probabilities for given sets of nuclear trajectories predict the observability of spontaneous positron emission in elastic collisions of heavy ions. These calculations are extended to the investigation of ratios $P_{y}(\eta)/P_{y}(1)$ for partial probabilities of positron emission at small positron energies. The results suggest a possible observability of spontaneous positron emission in elastic collisions of bare heavy ions by analyzing the slope of $P_{y}(\eta)/P_{y}(1)$ for values of $R_{min}$ $~_{\sim}\!\!\!\!^<$ 0.75 $R_{cr}$. In addition calculations of cross sections for positron emission in U+Cm and Cm+Cm collisions of fully ionized heavy ions are compared with former results with partly ionized projectiles and show an increase by factors of 57 to 72.