Spin–orbit ab initio investigation of the photodissociation of CH2Cl2

The photodissociation of dichloromethane (CH2Cl2) has been investigated by spin–orbit ab initio calculations. The potential energy curves were calculated by multi-state second order multiconfigurational perturbation theory in conjunction with spin–orbit interaction through complete active space state interaction (MS-CASPT2/CASSI-SO). The calculated results clearly assigned the experimentally observed photodissociation channels from the first and second singlet excited states leading to CH2Cl + Cl(2P3/2) and CH2Cl + Cl∗(2P1/2). The reason of higher Cl∗/Cl ratios in vibrationally mediated photodissociation than in vibrationless one was discussed.