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

We report strong isotope effects that influence the polarization of the spa tial distribution of the angular momentum j-vector of H-2(D-2) desorbing in the vibrational ground state from metal surfaces. For low final translatio nal energies, the j-vector distribution of desorbing H-2 shows a more helic opter-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 averagi ng over the Boltzmann distribution of total kinetic energies at surface tem peratures relevant to experiments, the resulting j-vector distribution of d esorbing H-2 shows a more helicopter-like rotational preference compared wi th desorbing D-2. (C) 1999 Elsevier Science B.V. All rights reserved.