Ultraviolet Photolysis Studies on XeO 4 in Noble‐Gas and F 2 Matrices and the Formation and Characterization of a New Xe VIII Oxide, (η 2 ‐O 2 )XeO 3

The photolytic behavior of the thermochemically unstable xenon(VIII) oxide XeO 4 was investigated by UV irradiation in noble‐gas and F 2 matrices. Photolysis of Xe 16 O 4 or Xe 18 O 4 in noble‐gas matrices at 365 nm yielded XeO 3 and a new xenon(VIII) oxide, namely, (η 2 ‐O 2 )XeO 3 , which, along with XeO 4 , was characterized by matrix‐isolation IR spectroscopy and quantum‐chemical calculations. Calculations of the UV spectrum showed that the photodecomposition is induced by an n→σ* transition, but the nature of the excitation differs when different light sources are used. There is strong evidence for the formation of mobile 1 D excited O atoms in the case of excitation at 365 nm, which led to the formation of (η 2 ‐O 2 )XeO 3 by reaction with XeO 4 . Matrix‐isolation IR spectroscopy in Ne and Ar matrices afforded the natural‐abundance xenon isotopic pattern for the ν 3 (T 2 ) stretching mode of Xe 16 O 4 , and 18 O enrichment provided the 16 O/ 18 O isotopic shifts of XeO 4 and (η 2 ‐O 2 )XeO 3 .