The 12B1, 12B2, 12A1, 12A2, 32A′(22B2), and 22A1 states of the 1,1-difluoromethane ion studied using multiconfiguration second-order perturbation theory

The 12B1(X2B1), 12B2, 12A1, 12A2, 22B2, and 22A1 states of the CH 2 F 2 + ion were studied using CASPT2 and CASSCF methods. Calculations suggest that one should consider the 32A′ state instead of 22B2. The CASPT2 T0 calculations predict the energy ordering of 12B1(X2B1), 12B2, 12A1, 12A2, 32A′, and 22A1, which is in line with the experimental results by Pradeep and Shirley. The CASPT2 T0 values for the 12B2, 12A2, 32A′, and 22A1 states are close to the experimental values. The F-loss and H-loss dissociation processes were studied at the CASPT2//CASSCF level. The energy levels of low-lying states of CH 2 F 2 + and CH 2 Cl 2 + are compared.