Infrared Spectrum and Structure of the Species CO3

Upon photolysis of solid CO₂ by 1216‐Å radiation, very high yields of CO₃ have been obtained. There is no evidence for the production of hydrogen‐containing species in experiments in which photolytically produced H or D atoms are also present. Experimental evidence supports a $C_{\text{2υ}}$ structure for CO₃ in its ground state, as predicted by molecular orbital calculations. The vibrational frequency pattern for the planar modes of isotopically substituted species of CO₃ has been fitted to a valence force potential having a minimal number of interaction force constants, assuming both an open structure having an O–C–O angle of 80° and a three‐membered ring structure having an O–C–O angle of 65°. Although the force constants obtained for the ring structure appear to be quite reasonable, exceptionally large values have been obtained for the O–C–O bending force constant and for all of the interaction constants for the open structure. On this basis, the three‐membered ring structure is favored for CO₃ in its ground state.