Formation of small lanthanum-carbide ions from laser induced fragmentation of LaatC82

The fragmentation behavior of the endohedral metallofullerene La@C₈₂ was studied using gas phase time-of-flight mass spectrometry. The results were compared with the fragmentation of C₆₀. When the metallofullerene was excited by a 337 nm ns laser, small lanthanum-carbide fragments LaCn+, n=0-6, were detected. A simple statistical maximum entropy model was used to simulate the excitation energy dependence of the loss of the LaCn+ molecules as well as C₂ evaporation to form smaller metallofullerenes. By comparing experimental ion intensities with the model, the appearance energies of LaCn+, n=0-6, were found to lie above 65 eV. The lanthanum-carbide fragments ejected from La_@^{C₈₂ decrease in size with increasing internal energy. The ejection of La+ and LaC2+} is preferred at the expense of larger fragments such as LaC4+ and metallofullerenes at the higher excitation.