Infrared Spectrum, Structure, Vibrational Potential Function, and Bonding in the Lithium Superoxide Molecule LiO2

Lithium superoxide has been synthesized by reacting lithium atoms and oxygen molecules at high dilution in inert and oxygen matrices. Isotopic substitution at all atomic positions and use of isotopic mixtures verify the molecular identity and indicate an isosceles triangular structure. Eighteen frequencies from six isotopic molecules determine the potential constants FO–O = 5.59 ± 0.05, FLi–O = 1.18 ± 0.02, and FLi–O,Li–O = − 0.21 ± 0.03 mdyn / Å. The oxygen–oxygen force constant for LiO2 coincides with that calculated for O2−, which suggests that the LiO2 molecule is highly ionic and may be considered as a lithium cation bonded to a superoxide anion by Coulombic forces.