Adsorption of 4He on carbon nanotube bundles

We have measured adsorption isotherms of helium on bundles of single walled carbon nanotubes (SWCNs) in the temperature range from 2 to 14 K. The isotherms and resulting isosteric heat suggest the bundles have sites with differing binding energy for adsorption on the first layer. The results are consistent with the standard interpretation that the bundles have high binding energy sites in either the interstitial channels or the grooves where two tubes meet on the external surface, and a lower energy, graphene like binding to the rest of the external surface. We present a comparison with results of experimental and theoretical studies on the same system. (C) 2003 Elsevier Science B.V. All rights reserved.