The initial dissociative sticking probability of ${\mathrm{H}}_2$ on Cu(110) has been measured using vibrationally hot, translationally cold-seeded beams. The results indicate a dissociative barrier which is accessed through energy partition in both translational and vibrational degrees of freedom in the im- pinging hydrogen molecule. The experiment has enabled a determination of the translational requirement in dissociating hydrogen in the first vibrational excited state, and the results place the barrier at ∼1 eV, in good agreement with theoretical predictions.

• Received 29 June 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.1823