VIBRATIONALLY ASSISTED STICKING, TUNNELING AND ISOTOPE EFFECT FOR HYDROGEN ON CU SURFACES

Using the reaction path description a model Hamiltonian is constructed for the strongly activated reaction of hydrogen molecules on Cu. Strong vibrational-translational coupling is found. This coupling manifests itself in vibrational heating in desorption and vibrationally assisted sticking in adsorption processes. The weak isotope effect in recently observed sticking data for H-2 and D2 can be reconciled with a strong one in desorption data by a proper choice of parameters of the model, in particular recent data on seeded beams may be explained by taking into account an appropriate change of the vibrational frequency along the reaction path.