Vibrational and electronic properties of hydrogen adsorbed on single-wall carbon nanotubes

The vibrational and electronic properties of hydrogen molecules adsorbed on single-wall carbon nanotubes were investigated by high-resolution electron-energy-loss spectroscopy. We found that the adsorption of H-2 molecules is dissociative at room temperature and 2.6x10(-2) Pa. The C-H bond formed upon hydrogen adsorption has a vibrational energy equal to 360 meV, in agreement with the expected sp(2)-sp(3) H-induced local rehybridization. The hydrogenation of carbon nanotubes also gives rise to significant changes for both the line shape and the excitation energy of the pi plasmon. Upon H adsorption, the plasmon shifts by 0.8 eV towards lower energies and, moreover, a weak feature rises up at 3.5 eV.