Gas-phase ion chromatography experiments with variable injection energ
ies were performed on C-7+ made by laser vaporization of graphite and
by collision-induced dissociation of C-10+ and C-12+. In all cases, th
e C-7+ cyclic isomer dominates over the linear isomer at lowest inject
ion energies, indicating the cyclic isomer is the most stable form. Th
is result is consistent with ab initio calculations and a kinetic mode
l developed here.