Positive and negative fullerene ions have been stored in a heavy-ion storage ring. We found confinement times (storage lifetimes) of the order of 2 to 10 s, the limit being set by colhsional destruction in the background gas. The data also show a short decay time of the order of some milliseconds. This component was considerably longer for the negative Cm and CT0 ions than the neighboring negative Cjs and Css ions. We discuss the possible processes that may account for the observation of the msdecay times. The present technique may provide an excellent way to produce and study cold clusters.
Lhtroduction
The structure and dynamic properties of the extraordinary stable and large carbon molecules, C6,, and C,,,, the so-called fullerenes [ 1 ] have attracted much attention during the last years. The field is growing rapidly, and the reader may consult refs. [2,3] for a review of the field. The stability of the various C, molecules is of major concern, and in much of the work reported in the literature estimates of various lifetimes related to the fullerenes are reported. Studies have shown that ion clusters continue to fragment for a long time after receiving additional internal energy. Evaporation times of the order of x: 100 us have been reported [ 4,5 1. C; and Cz-molecular ions, n = 7-28, produced by sputtering graphite were found to live at least 1 O-20 us [ 6 1. C& and C& were observed to live considerably longer than 1 ms [ 7 1. Delayed ionization with typical lifetimes on the order of several us was obtained in multi-photon ionization of CbO and &, [ 8,9]. It was found that the lifetimes were approximately equal for C6,, and C,O and depended on the number