The effect of glass transition in fullerite C60 on Ar impurity diffusion

The kinetics of sorption and subsequent desorption of argon gas by powdered C60 has been investigated in the temperature interval 58-290 K. The temperature dependence of the Ar diffusion coefficients in fullerite has been obtained using the measured characteristic times of sorption. The diffusion coefficients of Ar decrease monotonically with lowering temperature in the whole temperature range, what corresponds to the thermally activated diffusion of Ar atoms in fullerite. The glass transition in fullerite induces an order-of magnitude decrease in the activation energy of Ar diffusion in fullerite. This appears to be because of new directions appeared due to the glass transition in which the barriers separating the interstitial voids in the C60 lattice are significantly lower.