Volume 48, Number 3, November I 1999
|Page(s)||269 - 275|
|Section||Atomic and molecular physics|
|Published online||01 September 2002|
Quantum rotations in natural methane-clathrates from the Pacific sea-floor
Institut für Experimentelle und Angewandte Physik der Universität Kiel - Kiel, Germany
2 Institute Laue-Langevin - Grenoble, France
3 GEOMAR, Universität Kiel - Kiel, Germany
4 National Research Council of Canada - Ottawa, Ontario, Canada
5 Institut für Theoretische Physik I, Universität Erlangen-Nürnberg, Germany
Accepted: 2 September 1999
We report inelastic neutron scattering experiments from natural methane hydrates sampled from the Pacific sea-floor during an expedition of the research ship SONNE. The experiments verify directly the content of methane by measuring the rotational spectrum of the molecules. The existence of almost free rotational levels excludes off-center positions of the molecules in the cages. In addition we could assign the observed peaks in the energy regime up to 5 meV to rotational excitations only. The observed relative sharp excitations prove a surprisingly good crystallinity of the geological sample. The finite width is attributed to frozen-in hydrogen disorder of the ice cages.
PACS: 31.70.-f – Effects of atomic and molecular interactions on electronic structure / 36.20.-r – Macromolecules and polymer molecules / 33.20.-t – Molecular spectra
© EDP Sciences, 1999
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