Positron annihilation in hydrogen-doped alkali-metal fullerides

Abstract

Positron-annihilation / Alkali-metal-fulleride / Thermal-desorption / Raman-shiftSummary. Hydrogen-doped alkali-metal fullerides were studied by means of mass-analyzed thermal desorption and positron annihilation. The hydrogen desorption spectra reveal the inclusion of hydrogen in the fullerides as two types of components; one weakly adsorbed and the other strongly bound, probably as hydride ion. The positron lifetime spectra demonstrate that hydrogen-doping to alkali-metal fullerides increases a concentration of higher-order vacancy-type defects, through which more than 50% injected positrons decay with a lifetime of 0.42-0.71 ns.

Positron Annihilation in Alkali Metal-Doped Multiwall Carbon Nanotubes

“…We have studied the annihilation of positrons in monocrystalline graphite, 1) alkali metal-intercalated graphite, 2) fullerenes 3) and alkali metal-doped fullerene. 4,5) The shortest lifetimes observed for alkali metal-saturation-doped fullerides M 6 C 60 (M¼K, Rb, and Cs) are ascribed to the annihilation of positrons in a region where the wavefunctions of a positron and an electron overlap significantly, i.e. inside and around C 60 molecules.…”