Two-photon dissociation of paracyclophane and formation of p-quinodimethane by 193 nm laser photolysis

[2,2]Paracyclophane, 4,7-dimethyl[2,2]paracyclophane and 4,7,12,15-tetramethyl[2,2] paracyclophane were photolysed with an ArF laser in the gas phase. The two C–C bonds of these compounds dissociated and the corresponding p-quinodimethanes were observed in the transient spectra. Laser fluence dependence of the product indicated an efficient two-photon process. A hot molecule formed by internal conversion is proposed to be an intermediate for the two-photon dissociation.