Matrix effect on triatomic CO₂ molecule: Comparison between krypton and xenon.

Vibrational energies for low-lying levels of CO2 trapped in rare gas matrices are determined for four isotopic species by applying a theoretical model allowing contact transformation method to be applied as perturbation technique to the molecule trapped in a distorted lattice structure. Results are given for molecules trapped in krypton and xenon. For the latter, both face-centered-cubic (fcc) and hexagonal-closed-packed (hcp) structures are shown to be possible. New harmonic and anharmonic constants are determined that allows calculation of matrix dependent calculated energy levels. It is shown that if distortion of the lattice is calculated for one isopotomer, then it can be used to calculate vibrational energies of other trapped isotopic species. Changes are more significant for harmonic potential constants than for third order anharmonic ones. Calculated energy levels compare well with observed ones. Predictions of unobserved ones for the latter isotope and other species are also made. The values calculated for 13C16O2 are consistent with LIF experimental results