Spin and alignment effects in O₂ chemisorption on Fe(110), Ni(111), and Co(0001) films grown on W(110)

O₂ has a spin triplet multiplicity in its ground state, while the effect of its electron spin on O₂-surface interaction is not well understood. In this study, the spin and/or alignment effects in O₂ chemisorption on surfaces of Fe(110), Ni(111), and Co(0001) films grown on W(110) have been investigated with the use of a single spin-rotational state-selected O₂ beam. The results indicate that the spin effects for the Fe and Ni films are similar in that the initial sticking probability (S₀) of O₂ is higher when the spins of O₂ and the film are antiparallel, and the spin dependence in S₀, which amounts to 30%-40% at thermal energy, decays with increasing the O₂ kinetic energy (E₀). In the case of the Fe/O₂ system, however, considerable spin dependence was found to remain even at E₀ > 0.2 eV and on the oxidized surface. It has also been shown that the barrier for O₂ chemisorption increases in the order of Fe(110) < Ni(111) < Co(0001), and the difference in the observed alignment effect among the samples can be understood based on the difference in the barrier.