MATRIX-ASSISTED LASER DESORPTION IONIZATION TANDEM REFLECTRON TIME-OF-FLIGHT MASS-SPECTROMETRY OF FULLERENES/

A tandem reflectron time-of-flight mass spectrometer developed in our laboratory provides a unique opportunity to investigate the collision- induced dissociation of fullerene ions formed by matrix-assisted laser desorption/ionization (MALDI). Specifically, this opportunity arises from the ability to utilize high energy collisional activation (normal ly available only on tandem sector instruments by using continuous ion ization techniques) for ions formed by pulsed laser desorption, wherea s most MALDI time-of-flight instruments record product ion mass spectr a of ions formed by metastable or postsource decay. In this study we i nvestigate the products of mass-selected and collisonally activated C- 60(+) and C-70(+) ions by using different target gases over a range of target gas pressures. In general, heavier target gases produce more e xtensive fragmentation and improve the mass resolution of lower mass i onic products because a greater portion of these ions are formed by si ngle collisions. Additionally, the tandem time-of-flight instrument ut ilizes a nonlinear (curved-field) reflectron in the second mass analyz er that enables high energy collision-induced dissociation spectra to be recorded without scanning or stepping the reflectron voltage.