Molecular structure of the hydroperoxyl anion (HO₂^-)

The equilibrium geometry of ground state HO₂^-( ¹A′) has been determined by an ab initio multiconfiguration self-consistent field gradient optimization method using 14 active space molecular orbitals in a double zeta + polarization + (two different) diffuse Gaussian function basis sets. The calculated geometry is R (O-O) = 1.498 Å, R (O-H)=0.962 Å, and HOO=99.8°. For comparison purposes, parallel results were also obtained for the ground states of O, O^-, O₂, O₂^-, and HO². For a given basis set the calculated adiabatic electron affinities of O, O₂, and HO₂ are all found to differ by a constant value ±0.05 eV relative to their respective experimental values, suggesting that the errors in the molecular cases are essentially atomic in nature.