Time-resolved laser-induced incandescence (TR-LII) was applied for the detn. of particle sizes during carbon-particle formation from supersatd. at. carbon vapor that was generated by laser photolysis of carbon suboxide (C3O2) at room temp. Thus, the solid carbon particles were formed under hydrogen-free conditions. The TR-LII technique was used for in situ size measurement of growing carbon particles and samples of final particles were analyzed by transmission electron microscopy (TEM). It was found that the particles grow to a final size of 4-12 nm within 0.02-1 ms. The properties of the obtained particles depend on the initial conditions in the reaction vol., i.e. concn. of carbon suboxide, pressure and type of gas diluter, photolysis wavelength, and laser pulse energy. The comparison of TR-LII and TEM particle sizing results yields information about the effective thermal energy accommodation coeffs. for He, Ar, CO, and C3O2 mols. on carbon particles.