Gross and Scheffler Reply
  Among other things (e.g. steering and steric effects in dissociative adsorption) we had predicted that the initial sticking probability of H_2 molecules impinging at clean Pd(100) exhibits oscillations, reflecting the quantum nature of the scattering process. In the preceding comment Rettner and Auerbach (RA) analyze experimental results and conclude that these oscillations are not detectable and thus either not existing or at least very small. In this reply we argue that the experimental study of RA is not conclusive to rule out the existence of quantum oscillations in the scattering of H_2 and note several problems and incongruities in their study. 
Axel Gross and Matthias Scheffler