Possible Resonance in Positron-Hydrogen Scattering

The positron-hydrogen system is considered, with the view to determining whether a scattering resonance below the positronium threshold is likely to occur, as has been suggested by Bransden and Jundi. The likeliest mechanism for producing such a resonance would be the existence of a virtual bound state in the positronium-proton channel, brought about by the large dipole polarizability and mass of the positronium atom. A modification of Hol{}ien's technique enables one to reject spurious solutions without the use of the projection-operator technique. A nonvariational adiabatic calculation seems to indicate that a resonance does exist, lying at lying at 0.1 eV below the threshold. When, however, a variational treatment is employed, certain essential nonadiabatic terms appear. The resultant reduction in attraction serves to eliminate the apparent resonance. It is concluded that the previously reported resonance is probably an artifact.