Off-diagonal polarisation potentials in the e-H coupled-channels problem

Polarisation potentials, explicitly calculated for real channels outside the coupled space, have previously been included only for diagonal matrix elements in the momentum-space coupled-channels calculation. The effect of the inclusion of the polarisation terms in off-diagonal matrix elements is investigated for electron-hydrogen scattering in the 1s, 2s, 2p channel space at 54.42 eV.