Features of the fluorine‐substituted acetaldehydes dynamics in the low‐lying electronic states: Quantum mechanical study of the CHF₂CHO molecule lowest excited singlet state

Abstract

ABSTRACT:The potential energy surface (PES) for the CHF 2 CHO molecule in the excited S 1 state is calculated by the CASSCF method. The features of the 1-and 2-D cross-sections of PES are considered in comparison with those of the relative molecules. The vibrational frequencies are calculated in harmonic approximation and the vibrational energy levels for the inversion motion of the carbonyl fragment CCH a O and for the torsion motion of the CHF 2 -top are calculated in anharmonic approximation by the 1-and 2-D variational methods. The calculated data are compared with the experimental ones. The problems of the experimental data interpretation are considered.

Structure of the nitrosomethane molecule (CH3NO) in the ground electronic state: Testing of ab initio methods for the description of potential energy surface

“…As applied to the description of carbonyl molecules in the ground and excited electronic states, the CASSCF method has been found to be sufficiently stable and reliable when the active space consists of five valence molecular orbitals (MOs) localized predominantly on the carbonyl fragment CO 19–21. This is closely related to the fact that the electronic excitation of carbonyl systems RCHO is localized on the CO group (at least in low‐lying excited electronic states).…”

One-dimensional models of internal rotation in CX3NO molecules (X=H, D, F)

“…Test calculations of the related CClF 2 NO molecule, which is less rigid, in the harmonic approximation with inclusion of the zero-point energy correction, provided a poorer description of the potential. It should be noted that even in the case of internal rotation, the effective torsional potential may take exotic forms (see, for example, [18,35]). Hence, calculations of the torsional levels based only on the stationary points on the PES are of limited use.…”