Laser photolysis of trans-dichloroethylene at 193 nm: Quantum yields of photoproducts

The photodissociation of trans-dichloroethylene (trans-DCE) was studied using an ArF excimer laser at 193 nm. Acetylene, chloroacetylene and hydrogen chloride are observed as products, but the chlorine molecule is not observed. The yields are determined to be 0.47 ± 0.10 and 0.35 ± 0.05 for acetylene and chloroacetylene, respectively. On the basis of the reaction mechanism, the sum of the quantum yields of hydrogen chloride molecules (Φ = 0.35) and chlorine atoms (Φ = 0.94) dissociated from trans-DCE is estimated to be greater than unity. These results indicate that two chlorine atoms are successively dissociated from the parent molecule by the photolysis at 193 nm.