Towards the selective formation of specific isomers of fullerenes: T- and p-dependence in the yield of various isomers of fullerenes C-60-C-84

Systematic fractional change in the yield of various isomers of fullerenes was revealed to strongly depend on temperature of a buffer gas. A new kinetic consideration is proposed for understanding the observed temperature- and pressure-dependence of yield of fullerenes. The model consists of three competitive reactions in consideration of plausible behaviors of a precursor, (1) decomposition into smaller fragments, (2) isomerization leading to formation of a stable fullerene cage, and (3) growth into a larger carbon cluster. Arrhenius activation energy of formation of stable fullerenes was determined to be 0.8 eV for both C-60 and C-70, while a higher energy of 2.0-3.3 eV for seven different isomers of higher fullerenes ranging from C-76 to C-84 Correlation in the activation energy is noted for a series of higher fullerenes with different sizes, sugggesting the existence of a specific precursor in their formation processes.