The geometry of the ground state oxygen dimer ion (O2)+2 : T r a n s-planar or rectangular?

Abstract

Ab initio calculations on the O⁺₄ system, at the UMP3/6‐31G* level of approximation show that the electronic ground state of O⁺₄ favors a rectangular geometry (D_2h), over a trans‐planar geometry (C_2h), with the latter more energetic by 0.54 eV (12.5 kcal mol⁻¹). This result agrees with the conclusions of an ESR study on O⁺₄, but is in disagreement with the conclusions of a complementary IR study.