Binding energy predictions of positron- and positronium-atom systems

BINDING ENERGY PREDICTIONS OF POSITRONAND POSITRONIUM-ATOM SYSTEM Xiang Cheng, B.S. Marquette University, 2011 There has been a large amount of work studying positron and positronium (Ps) binding to atoms. Twelve atoms (including Ps) are known to bind with a positron and 14 atoms won’t. For Ps binding, 12 atoms are found to bind with Ps and 2 atoms do not. For both positron and Ps binding to atoms, we find that the known binding energy can be fitted to a simple expression involving several common physical properties. Positron binding energies can be fitted using the parameters of ionization potentials, polarizabilities, and the number of s electrons of the atoms; while Ps binding energies can be fitted using the covalent radii, the number of s electrons, and the product of ionization potentials and electron affinities. The fitted relationships are tested on the unbound atoms and bound atoms not involved in the fitting. Then these two best-fit equations are used to predict the binding energies of positron-atom and Ps-atom systems for all other unstudied atoms through Bi. The results are discussed and analyzed theoretically. The models and the results appear to be reliable.