Atomic and Molecular Physics Using Positron Traps and Trap-based Beams

Techniques to accumulate and cool positrons in Penning traps provide new tools to study atomic and molecular physics and chemistry. This chapter presents an overview of studies of the interaction of low-energy positrons with atoms and molecules using these methods. In the vacuum environment of a trap, isolated twobody interactions of positrons with atoms and molecules can be studied with precision. Measurements include annihilation rates, Zeff, as a function of both atomic and molecular species and positron temperature. Doppler-broadening studies provide information about the electronic states involved in the annihilation process. Positron accumulation techniques have also enabled the creation of cold, bright low-energy positron beams. High-resolution scattering measurements are described, including absolute measurements of the cross sections for vibrational excitation of molecules. Prospects for future developments in these areas are also discussed.