Observation of rotational excitations of H2 adsorbed on Ag surfaces

High-resolution electron-energy-loss studies of H2 on Ag at ∼ 10 K reveal both rotational and rotational-vibrational excitations of molecularly adsorbed and condensed H2. The rotational losses for submonolayers of adsorbed H2 indicate unhindered rotational motion as well as a H-H internuclear separation which is within ∼2% of that of condensed H2. Adsorbed H2 is also converted from predominantly orthohydrogen to parahydrogen. © 1982 The American Physical Society.