Reaction dynamics of the dichlorocarbene anion using tandem mass spectrometry

The dissociation dynamics of CCl₂^? anions were studied under various internal energy conditions. This study involved the measurement of daughter-ion spectra and branching ratios and of the amount of kinetic energy released (KER) on the fragments. The competition between C and Cl loss for CCl₂^? ions created by any of the following sequence of processes: (1) was particularly investigated. For process (1), the amount of fragmenting CCl₂^? ions is 8–10 times larger with Kr than with Xe or C₆H₆. The KER for Cl loss is smaller than 0.20 eV with the three target gases used. For the loss of C, the KER is much larger (0.7 eV). This KER is, however, equal to 0.21 eV for the collisionally activated C loss in process (2). For this latter process, the C loss vs. Cl loss branching ratio decreases with increasing internal energy. The KERs measured for process (3) are very similar to those obtained for process (1). It is suggested that repulsive or slightly bound excited states which correlate directly to the Cl₂^? (X²Σ_u⁺) + C asymptote and which are vibronically coupled to the ground state play an important role in these dissociation processes.