PHOTODISSOCIATION OF CLONO2 .1. ATOMIC RESONANCE FLUORESCENCE MEASUREMENTS OF PRODUCT QUANTUM YIELDS

The quantum yields for the production of Cl, O, and ClO in the photoly sis of ClONO2, measured by detecting Cl and O atoms by atomic resonanc e fluorescence, are reported. The resonance fluorescence signals were calibrated by generating known concentrations of Cl and O atoms from t he photolysis of Cl-2, HCl, O-3, or N2O. The quantum yields for Ci in the 193.2, 222.0, 248.25, and 308.15 nm photolysis of ClONO2 were 0.53 +/- 0.10, 0.46 +/- 0.10, 0.41 +/- 0.13, and 0.64 +/- 0.20, respective ly. The yields for O atoms at these wavelengths were, respectively, 0. 37 +/- 0.08, 0.17 +/- 0.05, <0.10, and <0.05. The quoted uncertainties are 2 sigma precision of the measurements. ClO radical was converted to Cl via addition of NO and its signal compared to the Cl atom signal produced by photolysis of ClONO2. The obtained quantum yields for ClO were 0.29 +/- 0.20, 0.64 +/- 0.20, 0.39 +/- 0.19, and 0.37 +/- 0.19, at 193.2, 222.0, 248.25, and 308.15 nm, respectively. It appears that Cl + NO3 and ClO + NO2 are the major products in the photodissociation of ClONO2, except at 193 nm. The measured quantum yields were found t o be independent of pressure (40-100 Ton) and bath gas (He and N-2). O ur results are compared with those from previous measurements.