Quantum rotation of hydrogen in single-wall carbon nanotubes

We report inelastic neutron scattering results on hydrogen adsorbed onto samples containing single-wall carbon nanotubes. These materials have attracted considerable interest recently due to reports of high density hydrogen storage at room temperature. Inelastic neutron scattering clearly shows the ortho-para conversion of physisorbed hydrogen in a nanotube containing soot loaded with hydrogen. From the rotational J = 0 --> 1 transition, no indication of a significant barrier to quantum rotation is seen. (C) 2000 Elsevier Science B.V. All rights reserved.