Multireference configuration interaction study of dichlorocarbene

- The equilibrium geometries and energies of seven electronic states of CCl2.
- The PESs of excited states correlated to the lowest three dissociation limits.
- The VTE, the oscillator strength, the configuration and the transition of each state.
- The discussion on the 248 nm photodissociation result.
- Assign the state excited by the 193 nm photon, determine the dissociation pathways.

Dichlorocarbene is an important reactive chemical intermediate, which has received much investigation. However, the energy, structure, and dynamics of the excited states are not well understood. Here, we investigated the equilibrium geometries and energies of seven electronic states, X̃1A1, Ã1B1, ã3B1, B̃1A2, b̃3A2, C̃1B2 and c̃3B2 of CCl2 using internally contracted multireference configuration interaction method including Davidson correction (icMRCI+Q) with different basis sets aug-cc-pV(X+d)Z(X = T, Q, 5), and the effects of different basis sets on the geometries and energies. For the first time, the theoretical studies of high excited singlet and triplet states of CCl2 that are related to the lowest three dissociation limits were carried out at the icMRCI+Q/aug-cc-pV(5+d)Z level. The results were compared with the previous experimental and theoretical data where available. Our results will add some understanding and shed some light on the structures and dynamics of electronic states of CCl2 radical.