We determine the exchange splitting in ferromagnetic Ni by means of angle-resolved photoemission from a (111) surface. The optical selection rules arising from use of the ($1\overline{1}0$) mirror plane of detection are used to identify the contributions from the majority- and minority-spin sub-bands. The splitting at the top of the $d$ bands turns out to be about 0.5 eV at the point $(0.14, -0.43, -0.43)\frac{2\pi }{a}$, in good agreement with a recent self-consistent band-structure calculation by Wang and Callaway based on the exchange potential of von Barth and Hedin.

• Received 2 November 1977

DOI:https://doi.org/10.1103/PhysRevLett.40.892