Neutron scattering studies of hydrofullerites hydrogenated under high hydrogen pressure

Complete text of publication follows. New hydroffullerites were obtained when the C60 fullerite was treated under a hydrogen gas pressure of 6 or 30 kbar at 620 K and quenched. A comparison between the inelastic neutron scattering (INS) spectra of the as-prepared samples and those after annealing at 300 K showed that the as-prepared hydrofullerites consisted of C60Hx molecules (with x ∼ 24 and 32 for the samples prepared at 6 and 30 kbar, respectively) and interstitially dissolved molecular hydrogen. Analysis of the INS spectra for the samples prepared at 30 kbar suggests polymeric binding of C60H32 in the hydrofullerite. Additionally, atomic (non-bound) hydrogen in endohedral positions is also likely. Neutron Compton scattering (the energy transfer of 3-50 eV and the momentum transfer of 30-130 A-1) on pristine C60, on polymeric (21 kbar) fullerite and on annealed C60H32 gave the carbon kinetic energies, respectively, 98, 101, and 123 meV. The carbon kinetic energy in the hydrofullerite is close to that in diamond (121 meV), this can indicate a marked hardening of C60H32. (author)