  The effects of confining molecular hydrogen within carbon nanohorns are
studied via high-resolution quasielastic and inelastic neutron spectroscopies.
Both sets of data are remarkably different from those obtained in bulk samples
in the liquid and crystalline states. At temperatures where bulk hydrogen is
liquid, the spectra of the confined sample show an elastic component indicating
a significant proportion of immobile molecules as well as distinctly narrower
quasielastic line widths and a strong distortion of the line shape of the para
- ortho rotational transition. The results show that hydrogen interacts far
more strongly with such carbonous structures than it does to carbon nanotubes,
suggesting that nanohorns and related nanostructures may offer significantly
better prospects as lightweight media for hydrogen storage applications.
