Positron state and Lifetime in C60/C70 Fullerites

ABSTRACTThe present paper reports on positron lifetime measurements on Ceo/C 70 fullerite powder as a function of temperature and quasi-hydrostatic pressure in order to give an estimate of the positron annihilation site in the fullerite lattice. A single-component positron lifetime of 402 ps is observed which significantly decreases under quasi-hydrostatic pressure. From this and the soft intermolecular properties of the fullerites one can conclude that the positron is annihilated rather in the intermolecular space than inside the fullerene molecules. However, positron trapping at lattice defects, which are observed by high-resolution electron microscopy, cannot be ruled out.