IDENTIFICATION OF THE NEUTRAL PRODUCTS FROM THE UNIMOLECULAR DISSOCIATION OF SINGLY AND MULTIPLY-CHARGED C-60 FULLERENE IONS

The neutral products eliminated upon the collisionally activated dissociation (CAD) of C-60(+z) ions (z = 1-4) are post-ionized to cations or anions and collected in neutral fragment-reionization ((+)N(f)R(+,-)) mass spectra. These spectra provide conclusive evidence that the decompositions C-60(+z) --> C-x(+z) + C-2n (where x > 30 and 2n < 30) proceed by cleavage of whole C-2n clusters, not consecutive losses of nC(2). As the charge of the fullerene precursor ion increases, the largest detectable neutral loss decreases, from C-28 for z = 1 to C-12 for z = 4. Post-ionization of C-2n to cations preferentially produces odd-carbon cluster ions (e.g., C-5(+), C-7(+), C-11(+), C-15(+)) whereas post-ionization to anions yields abundant even-carbon cluster ions (C-6(-), C-8(-)).