VIBRATIONAL AND TRANSLATIONAL ENERGY PARTITION AND THE BARRIER TO DISSOCIATIVE H-2 AND D2 ADSORPTION ON CU(110)

The initial dissociative sticking probability of H-2 and D2 on Cu(110) has been studied using hot nozzle and seeded supersonic molecular beams. Experiments with the pure beams indicate a higher sticking probability for H-2 over D2 at a particular translational energy or nozzle temperature. The relative contributions of vibrational and translational energy in accessing the barrier to dissociation is separated in vibrationally hot, translationally cold seeded beams. The results indicate a barrier which can be accessed through energy partition in both vibrational and translational degrees of freedom in the impinging molecule. The translational energy onset of the sticking of H-2(v = 1) = 130 meV, and for D2(v = 2) = 60 meV. The results are shown to be in excellent agreement with classical and quantum mechanical trajectory calculations on this surface based on a "late barrier" and a barrier height of 600-700 meV, near to the value predicted theoretically.