The highly excited vibrational energy levels of CO_2 up to 2000 cm~ (-1) have been studied in the Radau coordinates using the Lanczos algorithm and potential optimized discrete variable representation. The 500 levels below 20000 cm~(-1) are assigned with approximate normal mode quantum numbers. The Fermi resonance and anharmonicity of the high-lying vibrational levels have also been analyzed. Besides, the statistical distribution of the calculated energy levels shows that the vibrational spectra of CO_2 are largely regular in the energy range up to 20000 cm~(-1).

Key words: CARBON DIOXIDE, vibrational spectra, STATISTICAL DISTRIBUTION, EXCITED STATE