Resonance structure in the positron-hydrogen system above the ionization threshold

Positron scattering from atomic hydrogen is analysed above the ionization threshold and resonances for coupled-channels calculations comprising bases of up to three physical states of hydrogen H(1s,2s,2p) and three physical states of positronium Ps(1s,2s,2p) are determined. The calculations have been performed over the entire energy range from the ionization threshold up to a maximum incident positron energy of 4 Ryd. Additional resonances appear as the models increase in complexity. For the six-state model the authors report the identification of one new resonance for the J=0 partial wave, four for J=1, one for J=2 and one for J=3. No resonances are found in the higher partial waves. The positions and widths of the resonances are given.