1. Cryogenic NMR spectroscopy of endohedral hydrogen-fullerene complexes.
- Author
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Carravetta, M., Johannessen, O. G., Levitt, M. H., Heinmaa, I., Stern, R., Samoson, A., Horsewill, A. J., Murata, Y., and Komatsu, K.
- Subjects
LOW temperature engineering ,NUCLEAR magnetic resonance spectroscopy ,HYDROGEN ,FULLERENES ,CARBON ,NUCLEAR spectroscopy - Abstract
We have observed
1 H NMR spectra of hydrogen molecules trapped inside modified fullerene cages under cryogenic conditions. Experiments on static samples were performed at sample temperatures down to 4.3 K, while magic-angle-spinning (MAS) experiments were performed at temperatures down to 20 K at spinning frequencies of 15 kHz. Both types of NMR spectra show a large increase in the intramolecular1 H–1 H dipolar coupling at temperatures below 50 K, revealing thermal selection of a small number of spatial rotational states. The static and MAS spectra were compared to estimate the degree of sample heating in high-speed cryogenic MAS-NMR experiments. The cryogenic MAS-NMR data show that the site resolution of magic-angle-spinning NMR may be combined with the high signal strength of cryogenic operation and that cryogenic phenomena may be studied with chemical site selectivity. [ABSTRACT FROM AUTHOR]- Published
- 2006
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