A simple rate equation for fullerene coalescence

Recent experiments have demonstrated that large fullerenes can form by coalescence in the hot and dense vapor produced by pulsed UV-laser desorption of a fullerene film. The abundance spectra exhibit masses both at and close to the primary coalescence product. We suggest a rate equation that reproduces this pattern, applicable to the nearly symmetric abundance distributions observed in coalescence with high laser fluence and also to the strongly asymmetric case of coalescence with low fluence. The equation is parameterized by three rates, which in the completely symmetric and in the completely asymmetric case reduces to two. In these two cases the relative abundances can be expressed by a single dimensionless parameter.