Inelastic Neutron Scattering and Separation Coefficient of Absorbed Hydrogen: Molecular Alignment and Energy Levels

Inelastic neutron scattering and measurement of the ortho-para separation coefficient have been used to study the low lying rotational states of molecular hydrogen adsorbed on activated alumina. The observations are consistent with a picture in which the orientational motion of the molecules is severely hindered. Results are analyzed in terms of two models: a two-dimensional rotor and an axially constrained rotor. The latter which is more consistent with the data serves to explain preferential adsorption of orthohydrogen.