Quantum rotations in natural methane-clathrates from the Pacific sea-floor

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 $\rm CH_4$ molecules. The existence...

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Veröffentlicht in:Europhysics letters 1999-11, Vol.48 (3), p.269-275
Hauptverfasser: Gutt, C, Asmussen, B, Press, W, Merkl, C, Casalta, H, Greinert, J, Bohrmann, G, Tse, J. S, Hüller, A
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Sprache:eng
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Zusammenfassung: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 $\rm CH_4$ 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.
ISSN:0295-5075
1286-4854
DOI:10.1209/epl/i1999-00476-x