SEARCH FOR OSCILLATIONS IN THE TRANSLATIONAL ENERGY-DEPENDENCE OF THEDISSOCIATION OF H-2 ON PD(100)

Recent calculations of the variation of the probability of dissociativ e chemisorption, S-o, of H-2 on Pd(100) and on W(100) predict distinct oscillations in this probability with increasing translational energy , E(i), at low energy. We have searched for these oscillations in the H-2/Pd(100) system using a novel molecular beam scattering method. No oscillations could be found. We find that S-o falls monotonically with increasing E(i) up to similar to 0.1 eV. Any deviations from this mon otonic fall represent changes in S-o of < 1% and < 3% for H-2(J = 1, v = 0) and H-2(J = 0, v = 0), respectively, at a surface temperature of 80 K. We discuss the possibility that surface motion is responsible f or averaging away structure in S-o versus E(i).