Cage Destruction in Metal-Fullerene Clusters

Mass spectrometric studies on free clusters composed of single fullerene molecules and transition metal atoms ( ${\mathrm{C}}_{60}{M}_x$ and ${\mathrm{C}}_{70}{M}_x$; $x=0,\dots ,150\mathrm{}$, $M\in \{\mathrm{T}\mathrm{i},\mathrm{V},\mathrm{N}\mathrm{b},\mathrm{T}\mathrm{a}\}$) reveal that they undergo a laser induced transformation from metal-fullerene clusters to metal carbide and metallo-carbohedrene clusters. Two types of fragmentation behavior are observed. Fullerenes doped with titanium or vanadium seem to be stable at low laser intensities, whereas tantalum and niobium severely destabilize the fullerene cage. Photofragmentation spectra of preselected ${\mathrm{C}}_{60}{\mathrm{Ta}}_x$ indicate that the ${\mathrm{C}}_{60}$ cage is destroyed for $x\ge 3$.