Abstract
Necessary conditions for the existence of bound states for positron-atom systems are derived in terms of an adiabatic-type approximation by assuming that (i) their mutual potential energy has the form of a Morse potential and (ii) the first ionization energy of the atom exceeds the binding energy of an electron to a unit charge of infinite mass. Use is then made of the potential energies of the appropriate proton-atom systems, which have been determined by ab initio calculations or fitted to spectral or scattering data, to investigate the seven positron-atom systems to which the present theory is applicable. It is concluded that helium, nitrogen, and neon, in their ground states, should be incapable of binding positrons. Binding of positrons to hydrogen, oxygen, argon, and krypton, in their ground states, is not precluded by the theory, but the binding to krypton seems most likely.