The sign of the orientation parameter in electron-photon coincidence experiments

Steph et al. (1980) have proposed a model for the orientation parameter which attributes positive transfer of angular momentum to long-range attractive atomic polarisation potentials and negative transfer to electron-electron repulsion. This model is based on a classical grazing picture for the collision and has received considerable attention due to its intuitive appeal. The authors show that quantal calculations reveal that the physical effects of this model are not of primary importance in determining the sign of the orientation parameter.