Rotational polarization and filtering of hydrogen molecules by metal surfaces – isotope effects

Abstract

We report strong isotope effects that influence the polarization of the spatial distribution of the angular momentum j -vector of H 2(D 2) desorbing in the vibrational ground state from metal surfaces. For low final translational energies, the j -vector distribution of desorbing H 2 shows a more helicopter-like rotational preference compared with desorbing D 2. As the final translational energy increases, the j -vector distribution of desorbing H 2 eventually becomes more isotropic compared with desorbing D 2. Upon averaging over the Boltzmann distribution of total kinetic energies at surface temperatures relevant to experiments, the resulting j -vector distribution of desorbing H 2 shows a more helicopter-like rotational preference compared with desorbing D 2.