Positive and negative fullerene ions are produced coincidentally with impact ionization and attachment of electrons, and the generation of single pair-ion plasma is achieved. Because negative ions are accelerated by the electric field formed between a cathode and a grounded grid, they collide with positive ions, yielding the collision products as dimers. When the cathode setup is modified, double pair-ion plasmas are generated on each side and are miscible with each other. Both the ions are accelerated in the opposite direction by the electric field formed between two cathodes which can be diversely biased, and collide with each other, yielding effectively the collision products. This novel method without catalysts or nonallotropic fullerene derivatives has prospects of mass production of fullerene-fusion materials. (C) 2004 Elsevier B.V. All rights reserved.