ANOTHER S-WAVE RESONANCE IN POSITRON HYDROGEN SCATTERING

The close-coupling equations for the positron-hydrogen system restrict ed to s-wave scattering from the l = 0 levels of hydrogen and positron ium are written as a set of coupled momentum space Lippmann-Schwinger equations. The matrix element for positronium formation is evaluated b y integrating over the multipole projected components of the momentum space wave functions. Cross sections generated in the coupled static a pproximation provide a verification of the method. With a larger basis , including the 1s and 2s levels of hydrogen and the 1s and 2s levels of positronium, the broad s-wave resonance at 2.6 Ryd shifts position to 3.17 Ryd. An additional resonance is observed in the cross section at an energy of 1.10 Ryd.