MOLECULAR-STRUCTURE AND VIBRATIONAL INFRARED-SPECTRA OF FORMALDEHYDE, SELENOFORMALDEHYDE AND THEIR DIHALOGENODERIVATIVES BY AB-INITIO POST-HARTREE-FOCK CALCULATION

Results are presented from ab initio post-Hartree-Fock calculations for formaldehyde, selenoformaldehyde and their difluoro, dichloro and dibromo-derivatives. Molecular parameters (equilibrium geometries, dipole moments, rotational constants), and vibrational IR spectra (harmonic wavenumbers, absolute intensities) were calculated at the MP2 level with a triple-zeta valence shell basis set augmented by polarization functions on all atoms. Predicted molecular parameters and vibrational IR spectra agree very well with the experimental data. The shifts of the IR absorption bands upon isotopic substitution are also well reproduced by the calculations. Reported IR spectroscopic data and predicted molecular parameters might be applied to identification of the species for which experimental data are still elusive (e.g., CBr2Se) or incomplete (e.g., CCl2Se).