Raman spectroscopic investigation of H2, HD, and D2 physisorption on ropes of single-walled, carbon nanotubes -: art. no. 165502

We have observed the S - and Q-branch Raman spectra of H-2, HD, and D-2 adsorbed at 85 K and pressures up to 8 atm on single-walled, carbon nanotubes (SWNT). Comparative data for H-2 on graphite and C-60 were also collected. Frequency-downshifted and upshifted features were observed in the Q-branch spectra of H-2 on C-60 and SWNT. These shifts are small and are therefore inconsistent with charge transfer. An H-2 -surface potential with van der Waals and electrostatic terms was developed and used to estimate the shifts in the frequency of the Q(0) transition of H-2 adsorbed in two types of sites. These calculations corroborate the experimental findings and indicate physisorption in multiple sites of the SWNT ropes.