Formation of small lanthanum–carbide ions from laser induced fragmentation of La@C82

Abstract

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.