The soot volume fraction in low-pressure premixed flat flames is larger at the rim than at the axis, since the lower temperature at the periphery favors soot formation. On the other hand, there have been some very peculiar observations concerning large molecules and particles on the axis of benzene/oxygen flames: particles deposited through a molecular beam were considerably smaller than from acetylene flames. There were no charged soot particles, although the C/O ratio was well above the threshold value for soot formation. For these reasons the authors have studied the radial dependence of large ions and charged soot in a premixed benzene/oxygen flame. Large PAH are almost generally accepted as potential soot precursors. In the center of a sooting (at the rim) benzene flame they reach a much higher concentration than in a sooting acetylene flame, in which the soot is radially more evenly distributed. Yet the benzene flame does not form soot on its axis. There, the PAH are either oxidized, decompose, or form fullerenes but no soot. The results presented in this paper show that in benzene flames the homogeneous formation of fullerenes from PAH is preferred. In the center of these flames fullerenes are formed when themore » PAH concentration is a maximum in the oxidation zone. The high PAH concentration and the high temperature explain the high amount of fullerenes. In the cooler rim of the flame, large PAH molecules are not decomposed and form soot, as indicated by the charged particles, but the temperature does not reach values which are favorable for fullerene formation.« less