Photodissociation dynamics of carbonyl chloride fluoride and its implications for phosgene three body decay

The photodissociation dynamics of COFCl has been studied by monitoring Cl f ragments by resonance enhanced multi-photon ionisation and time-of-flight t echniques at dissociation wavelengths near 235 nm. The COFCl heat of format ion and the dissociation energy for C-Cl bond fission were for the first ti me experimentally determined: Delta(f) H-0(0) (COFCl) = -397 +/- 15 kJ mol( -1) and D-0(COF-Cl) = 364 +/- 8 kJ mol(-1). 35% of the available energy is channelled into FCO rotation and bending vibration. The remaining energy is released as product translation. Other than in phosgene, no spin-orbit sta te selective behaviour is observed. The observations agree with a decay mec hanism within the COFCl molecular plane as well as with a fragmentation via out-of-plane movement of the departing Cl atom. The structural and electro nic similarity of COFCl and COCl2 allows conclusions to be drawn on the COC l2 dissociation. The findings are evidence for a previously proposed decay mechanism for the asynchronous concerted three body decay of phosgene into CO + 2Cl. The first bond cleavage produces ground and excited spin-orbit st ate Cl and Cl*, respectively, with large kinetic energy release, while brea king the second C-Cl bond exclusively generates slow ground state Cl atoms.