Photolysis of carbon dioxide and methane mixtures at 873 and 293 K with 163.3 nm light

Abstract

Nearly all work with O(¹D) atoms has been conducted at room temperature. A system is described whereby photolysis of carbon dioxide at 163.3 nm may be used as a source of O(¹D) atoms at a range of temperatures extending above 873 K.

At 873 K the reaction of O(¹D) atoms with methane gave much the same products as O(³P) atoms, thus little or no methanol was found by stabilisation of the complex formed by an insertion reaction of O(¹D) atoms. The low quantum yields of oxygen which have often been reported in the photolysis of carbon dioxide can be caused by a carbon-containing surface layer.

The results favour an intermediate value for the rate constant of O(³P) with methane (k₂= 400 mol^–1 l. s^–1 at 293 K) and agree with relative rate constants for the deactivation of O(¹D) atoms at room temperature, obtained by Scott and Cvetanovic.