IR spectra of ozone adsorbed on MgO

The IR spectra of O-3 adsorbed on polycrystalline (high surface area) MgO are reported and assigned. Two distinct groups of absorptions in the 1160-970 and 1730-1170 cm(-1) spectral regions were observed. The bands falling in the first region, fully reversible upon decreasing the O-3 pressure, are grouped into two doublets with components at 1105-1024 cm(-1) (A(1)-A(3) doublet) and at 1140-1038 cm(-1) (B-1-B-3 doublet). The A(1)-A(3) doublet is assigned to the stretching modes (nu(sym) and nu(asym) respectively) of O-3 adsorbed through a terminal oxygen atom on Mg-5c(2+) ions exposed on the extended {001} terminations of the MgO microcrystals. The less intense B-1-B-3 doublet at 1140-1038 cm(-1) is assigned to the stretching modes of O-3 adsorbed on defective positions like edges, corners and steps. The irreversible bands in the 1730-1170 cm(-1) range are assigned to oxidation products formed by reaction of O-3 with carbonaceous impurities remaining on the MgO surface after the activation in vacuo at high temperature. In particular the doublet at 1690-1280 cm(-1) is assigned to the nu(asym) and nu(sym) stretching modes of bidentate carbonate-like species. The bathochromic shifts of the A(1)-A(3) components with increasing O-3 coverage are interpreted in terms of lateral dipole dipole interactions (of both static and dynamic nature) between the adsorbed species. The negative shift of the nu(asym) mode of the carbonate-like species induced by the increase in the O-3 coverage is ascribed to lateral interactions of the static type.