Abstract Previous workers have investigated the reaction of tetrachloroethene using thermal initiation and CO 2-laser initiation via sensitizing species. In both instances, the principal product was found to be hexachlorobenzene. One group reported evidence of laser specificity in this reaction, in that BCl 3 acted as a sensitizer to produce hexachlorobenzene as the principal product, but SF 6 and BBr 3 did not. We have found that specificity is ...