Search for oscillations in the translational energy dependence of the dissociation of H₂ on Pd(100)

Recent calculations of the variation of the probability of dissociative chemisorption, S0, of H2 on Pd(100) and on W(100) predict distinct oscillations in this probability with increasing translational energy, Ei, at low energy. We have searched for these oscillations in the H2/Pd(100) system using a novel molecular beam scattering method. No oscillations could be found. We find that S0 falls monotonically with increasing Ei up to ∼ 0.1 eV. Any deviations from this monotonic fall represent changes in S0 of < 1% and < 3% for H2(J = 1, v = 0) and H2(J = 0, v = 0), respectively, at a surface temperature of 80 K. We discuss the possibility that surface motion is responsible for averaging away structure in S0 versus Ei.