Fragmentation Mechanism of Fullerenes in the Positive and Negative Ion Channels

We have performed the photofragmentation studies of pristine C60 and C60/C70 composites on the reflectron time-of-flight mass spectrometer (RTOF MS) in the positive and negative ion channels. The mechanism of the formation of daughter fullerenes in the negative ion channel and the enhancement of fullerene coalescence reactions have been discussed and compared to our previous studies on the linear TOF. The 5 cm free expansion path in the RTOF experiments provides sufficient time and a favourable environment for the electrons to attach to the neutral daughter species, so it is thought to play a key role for the appearance of strong mass peaks of anionic fragmentation and aggregation fullerene products. The appearance of odd-numbered ``fullerene'' fragments is briefly discussed.