Quantum chemical studies of the potential energy surfaces and vibrational frequencies of the X(1A prime ), a(3A double prime ), and qq@(1A double prime ) states of CHCl and CFCl

The geometries, force constant, harmonic vibrational frequencies, and term energies of the X(1A prime ), a(3A double prime ), and qq@(1A double prime ), states of CHCl and CFCl, calculated by complete active space self-consistent field (CASSCF), complete active space second-order perturbation (CASPT2), and coupled cluster methods in conjunction with the correlation-consistent polarized valence triple-zeta (cc-pVTZ) basis set are reported and, where possible, compared with experimental data. As part of the study of the potential energy surfaces with respect to the CH and CCl stretches, the barriers to dissociation and linearity in the qq states have also been characterized. In the case of CFCl, which has been extensively studied experimentally, the computed spectroscopic constants in the X and qq states are in very good agreement with experiment.