INFRARED SPECTRA AND BONDING IN SODIUM SUPEROXIDE AND SODIUM PEROXIDE MOLECULES

Sodium superoxide has been produced for infrared spectral study by condensing sodium atoms and oxygen molecules at high dilution in argon on a CsI window at 15°K. Use of oxygen isotopic mixtures and comparison with lithium superoxide verify the molecular identity and indicate a symmetrical triangular structure. Nine frequencies from three isotopic molecules determine the potential constants FO-O = 5.46 ± 0.05, FNa-O = 0.80 ± 0.02, FNa-O, Na-O = -0.12 ± 0.02 mdyn/Å. The oxygen-oxygen stretching force constant for NaO2 is near those for LiO2 and O2- which suggests that the NaO2 molecule is highly ionic and may consist of a sodium cation bonded to a superoxide anion by coulombic forces. Further reaction of NaO2 with sodium atoms produces NaO2Na which has been identified and compared to lithium peroxide.