Theory of chemisorption of hydrogen on ferromagnetic substrates

We have developed a theory of chemisorption on ferromagnetic substrates in which the adsorbate and substrate electrons interact through a spin-spin interaction $J$. We also include the indirect interaction between adsorbates mediated by the substrate through $J$ and discuss the effect of surface spin waves and cooperative spin excitations of the substrate-adsorbate system on the density of states of the adsorbate. On the basis of this theory we can interpret the relative width, position, and shifts of the peaks in the reported ultraviolet photoemission spectra of H chemisorbed on Ni and Fe as well as their trend under varying surface coverage. We make detailed predictions about the magnetic structure of these spectra which would provide a clear test for distinguishing this theory from theories in which the adsorbate and substrate electrons are coupled through a hopping interaction.