The photodissociation of ClONO 2 at 235 nm was investigated using resonance enhanced multiphoton ionization time-of-flight mass spectrometry, which permits the state selective detection of Cl( 3 P 3/2 ) (Cl) and Cl( 3 P 1/2 ) (Cl*) atom products. The angular and speed distributions for the Cl, Cl*, and ClO channels were derived from forward convolution fitting of time-of-flight spectra. The anisotropy parameters for the Cl elimination channels are 0.5 ( 0.15 and 1.2 ( 0.15 for the atomic ground and excited states respectively, indicating that the states arise from different electronic excited states. The anisotropy parameter for the ClO + NO 2 channel is 1.0 ( 0.15. On the basis of simulations to the TOF data, we have determined a total Cl atom quantum yield of 0.42 ( 0.1 and a ClO quantum yield of 0.58 ( 0.1. The fraction of nascent NO 3 fragments that undergo secondary dissociation was calculated based on the measured internal energy distribution. The NO 2 + O channel has a quantum yield of 0.20, and NO + O 2 channel has a quantum yield of 0.006. The results are discussed in light of previous measurements at both longer and shorter wavelengths and suggest that at short wavelengths the spontaneous secondary dissociation of NO 3 to yield NO 2 + O is important and will substantially reduce the impact of the Cl + NO 3 channel on stratospheric ozone depletion.
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