1H MASNMR study of H2O absorbed in open single-wall C nanotubes (SWCNTs) of av. diam. 1.0 nm, synthesized with a Fe catalyst, was performed. Magic angle spinning significantly increases the spectral resoln. and the spectrum shows that there are at least 2 distinct chem. shift regions for the H2O proton. From temp. dependent measurements, the authors assign the 2 chem. shift ranges to H2O absorbed inside and outside the nanotube. The spectra as a function of the H2O content show that the 1st H2O mols. that are absorbed by the dry material are absorbed inside the tubes.