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Helium-3 nuclear magnetic resonance (3He-NMR) is an analytical technique used to identify helium-containing compounds. Because a helium atom, or even two helium atoms, can be encased in fullerene-like cages, the nuclear magnetic resonance spectroscopy of this element can be a sensitive probe for changes of the carbon framework around it.[1][2] Using carbon-13 NMR to analyze fullerenes themselves is complicated by so many subtle differences among the carbons in anything but the simplest, highly-symmetric structures. The technique is limited by the need to use the rare helium-3 isotope: the vast majority of naturally occurring helium is helium-4, which does not have suitable magnetic properties for NMR detection.

References

  1. ^ Saunders, Martin; Jimenez-Vazquez, Hugo A.; Bangerter, Benedict W.; Cross, R. James; Mroczkowski, Stanley; Freedberg, Daron I.; Anet, Frank A. L. (1994). "3He NMR: A Powerful New Tool for Following Fullerene Chemistry". Journal of the American Chemical Society. 116 (8): 3621–3622. doi:10.1021/ja00087a067.
  2. ^ Institute of Chemistry, The Hebrew University of Jerusalem. "(3He) Helium NMR".


source: http://en.wikipedia.org/wiki/Helium-3_nuclear_magnetic_resonance