Adsorption of argon on carbon nanotube bundles and its influence on the bundle lattice parameter.

We report experimental studies of the adsorption characteristics and structure of both 36Ar and 40Ar on single-wall carbon nanotube bundles. The structural studies make use of the large difference in coherent neutron scattering cross section for the two Ar isotopes to explore the influence of the adsorbate on the nanotube lattice parameter. We observe no dilation of the nanotube lattice with 40Ar, and explain the apparent expansion of this lattice upon 36Ar adsorption by the location of the adsorbed Ar atoms on the outer bundle surface.