MEASURING THE POSITRON AFFINITIES OF ATOMS

It is proposed that the binding energies of positrons to a number of atoms be determined by the charge transfer reaction A-+e+ Ae++e-. This reaction can be realized in the laboratory by directing a negative ion beam through a positron trap and measuring positively charged ions downstream. Unique identification of Ae+ is possible when the electron affinity, positron affinity and neutral atom ionization potentials satisfy a few simple identities. This technique could be used to investigate the existence of positron binding for a number of elements such as Si, Fe, Cu, Ge, Ru, Ag, Sn, Sb, Ta, W, Au, Pb and Bi.