Photochemical Decomposition of RuO4

Article abstract of DOI:10.1021/j100369a039

For the first time, the photochemical decomposition of gaseous RuO4 as a function of wavelenght has been studied.Two types of studies were employed: (a) irradiation with a constant-intensity mercury arc, isolating lines with filters, and (b) flash photolysis and kinetic absorption spectroscopy using a xenon flash lamp and liquid solution filters.The steady mercury arc irradiation gave quantum yields as a function of wavelength, and the flash photolysis experiments gave spectra of previously unreported products.Photochemical reactions of RuO4 have been determined for three spectral regions: (I) 440 - 370, (II) 370 - 320, and (III) 320 - 240 nm.For (I) the product is a solid, thin film of RuO3 deposited on the cell wall, and the quantum yield is 0.05; for (II) the product is a solid RuO2 aerosol with submicron-sized particles, and the quantum yields are 1.0 - 1.2; for (III) both RuO3 and RuO2 are formed simultaneously in the forms described above, and in addition, on a microsecond time scale, absorption spectra of gaseous RuO and Ru are observed.These results are interpreted in terms of two thresholds for predissociation or, more likely, vibrationally hot molecule dissociation, one at ca. 370 nm for dissociation to O2 and RuO2 and another at ca 320 nm for breaking a single Ru-O bond.The observed threshold energies agree well with thermodynamic estimates.The production of RuO and Ru species is attributed to secondary dark reactions involving O atoms.