ISOMERS OF SMALL CARBON CLUSTER ANIONS - LINEAR-CHAINS WITH UP TO 20 ATOMS

The structure of small carbon cluster anions, C(n)- (4 less-than-or-equal-to n less-than-or-equal-to 20), was investigated with the use of ion chromatography. With this technique, both the existence and the relative amounts of possible structural isomers can be determined. More than 99% of the ions C5- to C-9- were found to be linear under these experimental conditions. Starting with C-10-, a monocyclic isomer was observed, and linear and moncyclic structures coexisted from C-10- through at least C20-. This result is in contrast to previous work on positive ions, which showed the existence of linear isomers from C5+ to C-10+, with linear and cyclic isomers coexisting only from C-7+ to C-10+ Above C-10+, no linear clusters were observed.