A new route for fullerene synthesis by CO2-laser pyrolysis of gas phase mixture is proposed. Small hydrocarbon molecules which absorb the laser radiation, such as butadiene, are mixed with nitrous oxide (N2O) as oxidizer. Such a mixture allows avoiding the use of a photosensitizer as SF6 which causes contamination of the reaction zone and possibly influences the growth of fullerenic structures. This Letter also confirms the strong influence of the C/O atomic ratio in the mixture on the fullerene yield, and shows that residence time of the reactants in the pyrolysis flame and pressure influence dramatically the fullerene formation. (C) 2003 Elsevier B.V. All rights reserved.