INFRARED-SPECTRA AND QUANTUM-CHEMICAL CALCULATIONS OF GROUP-2 MO(2), O(2)MO(2), AND RELATED MOLECULES

Laser-ablated group 2 metal atoms have been reacted with O-2 in conden sing N-2 to complement earlier Ar studies owing to different relaxatio n dynamics of N-2 and Ar with respect to excited metal atoms and ionic product molecules. In the case of Ca + O-2, the reaction in condensin g Ar gives primarily the B-3(2) Open bent OCaO dioxide product, but th e reaction in condensing N-2 favors the (1)A(1) cyclic CaO2 peroxide s pecies. Three fundamentals are observed with O-18 and Ca-44 substituti on for CaO2, and isotopic frequencies are in excellent agreement with the predictions of quantum chemical calculations. Although DFT/B3LYP f requencies are slightly higher than MP2 and CASSCF values, a similar p attern is calculated. Ionic molecules interact more strongly with a ni trogen matrix than with argon, and calculations of N(2)MO(x) and ArMO( x) molecules can be used to explain matrix shifts. Several N(2)MO(2) s pecies are formed spontaneously from MO(2) molecules in solid nitrogen , and a match is found for observed matrix and DFT calculated isotopic frequencies. By comparison, the new molecule ArBeO2 is identified in earlier argon matrix experiments. The new metal disuperoxide molecules , O(2)MO(2), are also identified here. Calcium disuperoxide, O2CaO2, i s characterized as a D-2d species with +1.12 charge on Ca and -0.28 on each O, in contrast to calcium peroxide, CaO2, a C-2v molecule with 1.05 charge on Ca and -0.525 on each oxygen atom.