The time dependence of the decay of dark electrical conductivity of C60 crystals was investigated. The decay time constant was fitted by using the least-squares method and the diffusivity was calculated (table 10). It was suggested that the decay of electrical conductivity could be fitted by a stretched exponential function which indicated that O2 diffusion in C60 crystal obeyed a hierarchically constrained dynamic. The corresponding value of diffusivity was also estimated on the basis of the fitted decay-time constant.

Diffusion of O2 in C60 Crystal by Measuring the Decay of Electrical Conductivity. Yang, C.M., Liao, J.L., Chiu, K.C.: Journal of Applied Physics, 2004, 96[4], 1934-8