Springer LINK: The European Physical Journal B - Abstract Volume 3 Issue 1 (1998) pp 109-117

The European Physical Journal B

ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)

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Abstract Volume 3 Issue 1 (1998) pp 109-117

Inelastic neutron scattering from $\mathsf{H_2}$ on vapour deposited $\mathsf{CO_2}$

A. Knipp (1) (a), W. Langel (1) (b), H. Mutka (2), E. Knözinger (1) (c)

(1) Fachbereich Chemie der Universität Siegen, 57068 Siegen, Germany
(2) Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France

Received: 15 October 1996 / Revised: 25 August 1997 / Accepted: 24 October 1997

Abstract: 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[:AND:] 68.35.Ja Surface and interface dynamics and vibrations - 33.15.Fm Bond strengths, dissociation energies

(a) Present address: Edwards Hochvakuum GmbH, 85551 Kirchheim/Munich, Germany
(b) email: langel@chem735.chemie.uni-greifswald.de
(c) Present address: Institut für Physikalische Chemie der Technischen Universität Wien, Getreidemarkt 9, 1060 Wien, Austria

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