Molecular fusion of(C60)Nclusters in the gas phase after femtosecond laser irradiation

We report observation of molecular fusion of $\left({\mathrm{C}}_{60}\right)_N{}^{+}$ clusters to form large fullerene molecules after excitation by 800-nm femtosecond laser pulses. The fused species decay by undergoing ${\mathrm{C}}_2$ fragmentation. Such fragmentation behavior for excited clusters of fullerene molecules can be understood in terms of the energetics of molecular fusion as determined previously from fullerene-fullerene collision experiments. Within a certain excitation energy window, there is sufficient time for a substantial atomic rearrangement to take place within the clusters before they dissociate. Below this energy window there is not sufficient internal energy for molecular fusion to occur while above the energy window multiple ionization followed by breakup of the clusters dominates.