MOLECULAR MODULATION KINETIC SPECTROMETRY . C100 AND C102 RADICALS IN PHOTOLYSIS OF CHLORINE IN OXYGEN

By means of the new molecular modulation method, the gas-phase absorption spectra of the peroxyl radical ClOO has been observed between 2300 and 2600 Å (ultraviolet) and between 1430 and 1460 cm−1 (infrared). This radical was produced by the photolysis of Cl2 in the presence of O2. The ultraviolet spectrum of the CIO radical was also observed, but its infrared spectrum could not be obtained by this method. By direct observation of these two intermediates, a detailed kinetic study was. carried out, in which radical half-lives were inferred from observed phase shifts between the square-wave photolyzing light and the radical concentration. To enhance the weak signals from the low concentration radicals, the data were put in digital form and long-term averaging was carried out. The mechanism built up by previous workers was modified slightly to give a ten-step mechanism, which is in excellent agreement with observations. By combining other rate measurements, thermodynamic data, and the present results, seven out of the ten elementary rate constants were evaluated, and a product-and-ratio of the other three was evaluated as one term. The absolute cross section for absorption of infrared and ultraviolet radiation by ClOO was determined. © 1969, American Chemical Society. All rights reserved.