Dipole oscillator strength distributions,sums, and dispersion energy coefficients for CO and CO2

Globally reliable dipole oscillator strength distributions (DOSDs) have been constructed for ground state CO and CO₂ molecules; the DOSD for CO corresponds to photon energies greater than the electronic absorption threshold while that for CO₂ includes the infrared part of the spectra as well. The recommended DOSDs are used to evaluate the isotropic dipole—dipole dispersion energies for the COCO, COCO2 and CO2CO2 interactions as well as the molar refractivities, as a function of wavelength, and the dipole sums, S_k, k = 2(?1) -4, -6, -8, -10, for the two molecules. Pseudo-DOSD representations of the recommended DOSDs are provided which allow the efficient accurate evaluation of the dispersion energy coefficients C₆ for the interaction of CO or CO₂ with a variety of other atoms and molecules. Previous results for C₆ are found to be in disagreement with our recommended results for interactions involving CO₂. The results of this paper are used to give a reasonably general discussion of the difficulties associated with obtaining reliable results for C₆ by using Padé approximant bounding methods.