ON THE SELECTION OF ELECTRON BEAMS FOR THE INTENSITY CALCULATION OF OFFNORMAL PHOTOELECTRON DIFFRACTION

It is shown that the circle of electron beams will be shifted when off-normal photoelectron diffraction (OFF-NPD) instead of the normal photoelectron diffraction(NPD) is used. For the C(2x2)Se-Ni(001) system, the I-E curves of OFF-NPD has been calculated in terms of the shifted circle to select beams in the case of θ=36°. The correct structure constants of surface have been determined, which confirmed earlier NPD and OFF-NPD experimental results.