High yield production of C74 using an arc-discharge plasma

Carbon soot is produced under various conditions of an arc-discharge plasma in a helium atmosphere and its mass analysis is performed in detail by a laser-desorption time-of-flight spectrometer in order to clarify production ratios of higher fullerenes to C-60. It is found that the helium-gas pressure P-He has a strong effect on the production ratio. In a low pressure region (P-He < 100 Torr) C-60 and C-70 are first and second in production quantity, respectively and the quantities of the other higher fullerenes are negligibly small. When P-He is increased (100 less than or similar to P-He < 500 Torr), C-74 turns out to be efficiently produced and comparable to C-70 in production quantity. In a higher pressure region (P-He greater than or similar to 500 Torr) the production quantity of C-74 is the largest in the higher fullerenes, which almost attains that of C-60. The overall production ratio is estimated to be in the order, C-60, C-74,C- C-70, etc. This high-yield C-74 production seems to be related to charged-particle dynamics in the are-discharge plasma. (C) 1998 Elsevier Science S.A.