Photofragmentation of C-60 in seeded supersonic molecular beams: Effects of ro-vibrational cooling

Experiments in He seeded C60 supersonic beams show that multiphoton ionization and fragmentation are strongly affected by the initial ro-vibrational state of fullerene. The cooling generated by the supersonic expansion induces a higher rate of fragmentation and a significant shift of the barycenter of the mass distribution toward smaller fragments. The competition between the different decay channels results to be strongly affected. Our findings suggest that a purely statistical description, which is commonly assumed, could be inadequate and that processes involving the phonon coupling with collective electronic excitation play an important role in governing the access to different decay channels.