Knowledge Bank

When solid carbon dioxide at $77\circ K$ is irradiated with vacuum ultraviolet radiation from a xenon discharge lamp, new absorption bands at 2045, 1880, 1073, and $972cm-1$ appear in the infrared spectrum of the solid, along with a band at $2139cm-1$ due to CO. Results of experiments using carbon dioxide enriched in $C13$ or $O18$ indicate that the new features arise from the molecule $CO3$ and that this molecule probably has a planar, symmetrical structure of $D3h$ symmetry. An assignment of frequencies to the normal modes of $CO3$ is proposed. Carbon trioxide appears to be easily decomposed photolytically.