https://doi.org/10.1007/s100510050289
Inelastic neutron scattering from H2 on vapour deposited CO2
1
Fachbereich Chemie der Universität Siegen, 57068 Siegen, Germany
2
Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
Corresponding author: a langel@chem735.chemie.uni-greifswald.de
Received:
15
October
1996
Revised:
25
August
1997
Accepted:
24
October
1997
Published online: 15 May 1998
Inelastic neutron scattering spectra at 17 meV and 68 meV incident energies of molecular hydrogen adsorbed on vapour deposited substrates of pure CO2, 90:10 and 50:50 CO2:Kr are reported. The ortho-para transition is shifted from 14.7 meV in the free H2-molecule to 9.4 meV in a presumably commensurate ortho-H2 monolayer on the CO2 surface. The quadrupole-quadrupole interaction of ortho-H2 molecules with the CO2 substrate results in a strongly anisotropic potential. In addition to rotations the dynamics of this layer comprise a local Einstein mode and phonons in resonance with the substrate, giving rise to intense multiphonon transitions. Quasielastic scattering on warmer samples is assigned to a liquidlike adsorption layer, in which the H2 rotations are strongly perturbed.
PACS: 29.30.Hs – Neutron spectroscopy / 68.35.Ja – Surface and interface dynamics and vibrations / 33.15.Fm – Bond strengths, dissociation energies
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998
