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RESEARCH PRODUCT

The influence of the trapping potential on the attachment of a second electron to stored metal cluster and fullerene anions

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Abstract Singly charged anionic clusters are exposed to a bath of simultaneously stored electrons in ion cyclotron resonance (Penning) traps and thus, dianions are produced. The dianion yield is found to be a function of the potential well depth. As an example, the attachment of electrons to size-selected gold cluster anions Au 25 1− from a laser vaporization source has been studied in detail by time-of-flight mass analysis after ejection of all ions from the trap. Furthermore, the investigation is extended to fullerene anions C 70 1− that are produced by laser desorption from a fullerene target in the external source of a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. As in the case of metal cluster dianions, the possibility to add another surplus electron depends on the potential well depth, presumably due to the repulsive Coulomb barrier for electron attachment. The threshold of the potential well depth has been determined to be about 2.5 V for the production of Au 25 2− in a hyperbolical Penning trap and 5.8 V for the formation of C 70 2− in a cylindrical FT-ICR trap.