Reinterpretation of a controversial structure in the photoemission spectrum of Ni(001) by spin analysis

We have performed spin-polarized angle- and energy-resolved photoemission measurements on Ni(001) with polarized He I radiation ($h\nu =21.22\mathrm{}$ eV). The energy-distribution curves show a shoulder which has been interpreted heretofore as a ${\overline{\Gamma }}_5$ majority-spin surface state. This surface state was assumed to determine the spin polarization of earlier photoyield measurements near threshold. Our spin-resolved measurements demonstrate, however, that this structure is due to minority-spin emission in contradiction to the earlier assignment. Investigations of the light-polarization dependence, as well as of small deviations from normal-emission conditions in conjunction with photoemission calculations, show that the main contributions to the observed structure are due to off-normal emission from the ${\Delta }_2$ band. It is concluded that contributions from surface structures can only be of minor importance.