Kinetics of XeO4 decomposition and mechanism of atomic oxygen interaction with xenon tetraoxide in gas phase

The rate constant for decomposition of xenon tetraoxide in a helium atmosph ere in the presence of a quartz surface, which turned out to be nearly firs t order in the XeO4 concentration (n=1.2), is determined spectrophotometric ally from a decrease in the optical density of XeO4, k(0) (292 K)=(4.9+/-0. 5).10(-5) s(-1). Reactions O+XeO4 -->2O(2)+O+Xe (2a), O-2+3O+Xe (2b), O-2+O -3+Xe (2c), and O-2+XeO3 (2d) are studied under conditions of no heterogene ous processes by probing a diffusion cloud in a helium flow and monitoring the reagents and products by means of mass spectroscopy. The overall rate c onstant is assessed from the relative consumption rate of XeO4, k(2)(303 K) =(2+/-1).10(-14) cm(3)/s. The temperature dependence is derived from the ac cumulation rate of the product Xe, k(2a)+k(2b)+k(2c)=1.5.10(-11) exp(-2000/ T) [cm(3)/s]; (k(2a)+k(2b)+k(2c))(303 K)=(2+/-0.4).10(-14) cm(3)/s. The rat e constant for reaction (2d) is assessed from the condition that no traces of another product - XeO3 were detected, k(2d)(287 K)<5.10(-15) cm(3)/s.