The Stationary States of Adsorbed Hydrogen

In order to investigate the impact of quantum effects on hydrogen adsorption, it is important to understand the stationary states occupied by adsorbed hydrogen molecules. We present experimental inelastic neutron scattering spectra which provide evidence for significant mixing of degrees of freedom which are normally decoupled in free space. Results suggest that simultaneous treatment of translational and rotational degrees of freedom and consideration of the potential corrugation are necessary for improved theoretical understanding of the problem. Numerical calculations of the full five dimensional single body potential are used to understand the origins of the experimentally observed stationary states. In addition, we briefly discuss how our results may be used to understand the shape of hydrogen adsorption isotherms.