Structure of CuO₂ and its photochemistry in rare gas matrices

Photolysis of rare gas solid deposits containing Cu atoms and molecular oxygen results in formation of a CuO₂ oxide. Vibrational analysis shows that the molecule does not contain a peroxidic bond but has a linear, centrosymmetric O=Cu=O structure with, in a formal sense, tetravalent copper. The CuO₂ molecule is characterized by ground-state vibrational frequencies ν₁″ = 610 cm^-1 and ν₂″ = 193 cm^-1 and has two low-lying electronic states near 3850 and 20 700 cm^-1, respectively. The CuO₂ formation and its electronic structure are discussed. A weak, long-lived emission with origin at ∼15 500 cm^-1 and ν″ ∼625 ± 5 cm^-1 is also observed and shown to be probably due to diatomic CuO.