CASPT2 study of the electronic states of chlorodifluoromethane and chlorofluoromethane ions

Abstract

We performed CASPT2 geometry optimization and energetic calculations for the six lowest-lying states of and the seven lowest-lying states of CH₂ClF⁺. Based on the CASPT2 energetic calculations, we assign the X, A, B, C, D, and E states of to 1²A′, 1²A", 2²A′ (repulsive), 2²A", 3²A′, and 3²A", respectively, and the X, A, B, C, D, E, and F states of CH₂ClF⁺ to 1²A", 1²A′, 2²A′ (repulsive), 2²A", 3²A′, 3²A", and 4²A′, respectively. The CASPT2 relative energies (T _v′) for these electronic states of the two ions are in good or reasonable agreement with recently reported experimental data. For each of the two ions the geometries of the ionic states are significantly different (in a different manner) from the geometry of the parent molecule, and our preliminary explanations for some of the geometric changes in the ionic states are given. We also performed CASPT2//CASSCF potential energy curve calculations for Cl-loss dissociation from the six lowest-lying states of and the four lowest-lying states of CH₂ClF⁺, and the calculations indicate that the dissociation products for all these states, except 2²A" of , are the Cl atom plus the or CH₂F⁺ ion in the different states. The products for 2²A" of are the Cl⁺ ion plus CHF₂. The CASPT2//CASSCF appearance potential values for (1¹A₁) and CH₂F⁺ (1¹A₁) are very close to recently reported experimental data.

Keywords:

• CHClF₂ ⁺
• CH₂ClF⁺
• Electronic states
• Dissociation
• CASPT2

Acknowledgement

This work was supported by the National Natural Science Foundation Committee of China (No. 20333050).