Strong rotational effects in the adsorption dynamics of H2/Pd(111): evidence for dynamical steering

We have used seeded beam techniques to determine the influence of the rotational energy of hydrogen and deuterium molecules on the adsorption dynamics. A strong decrease of sticking with increasing rotational energy has been observed. In the low translational energy regime where the sticking coefficient decreases with beam energy the strongest effects are encountered. This result points to the importance of dynamical steering rather than to adsorption via a classical molecular precursor. Because rotational energy is quantized, clear isotope effects between hydrogen and deuterium can be observed.