Photofragmentation study of metal fullerides C60Mx (M=Sm, Pt, Ni and Rh) by excimer laser ablation-TOF mass spectrometry shows that metallofullerenes C2nM and C2n+1M formed in both the positive and negative ionic modes. The isotopic distributions of the metallofullerenes C2nM and C2n+1M are consistent with the calculated spectra based on the natural abundance of isotopes of C and M, confirming the formation of metallofullerenes. The metal atom is sup-posed to be incorporated into the network of the fullerene cage to replace one carbon atom of the cage forming substi-tutional metallofullerene. Odd-numbered high carbon clusters are observed in our laser ablation study of all the metal fullerides in the negative ion channel. Evolution of mass spectrum with irradiation laser shots shows that the formation of the substitutionally doped fullerenes is closely related to the production of metal carbide (MC). The structures, as well as formation mechanism, of metallofullerenes C2n+1M and C2nM with even and odd nu Photofragmentation study of metal fullerides C60Mx (M = Sm, Pt, Ni and Rh) by excimer laser ablation-TOF mass spectrometry shows that metallofullerenes C2nM and C2n + 1M formed in both the positive and negative ionic modes. The isotopic distributions of the metallofullerenes C2nM and C2n + 1M are consistent with the calculated spectra based on the natural abundance of isotopes of C and M, confirming the formation of metallofullerenes. The metal atom is sup-posed to be incorporated into the network of the fullerene cage to replace one carbon atom of the cage forming substi-tutional metallofullerene. Odd-numbered high carbon clusters are observed in our laser ablation study of all the metal fullerides in the negative ion channel. Evolution of mass spectrum with irradiation laser shots that the formation of the substitutionally doped fullerenes is closely related to the production of metal carbide (MC). The structures, as well as formation mechanism, of metallofullerenes C2n + 1M and C2nM w ith even and odd nu