Absolute quantum yields Phi(Cl+Cl*) for the formation of chlorine atoms were measured under collision-free conditions for the gas-phase dissociation of carbon tetrachloride (CCl4) after pulsed laser photoexcitation at 193 and 135 nm. By means of a photolytic calibration method, where the gas-phase photolysis of HCl was utilized as a reference, values of Phi(Cl+Cl*) (193 mn) = 1.5 +/- 0.1 and Phi(Cl+Cl*) (135 nm) = 1.9 +/- 0.1 could be obtained which demonstrate the importance of the ultraviolet (UV) and vacuum-UV photolysis Of CCl4 as an efficient source of atomic chlorine formation. (C) 2002 Published by Elsevier Science B.V.