Electron paramagnetic resonance study of hydrogen and fluorine atom addition to SO2

The electron paramagnetic resonance spectrum of the species formed in the near uv photolysis of mixtures of argon or krypton containing 1% HI and SO2, 1% CF3OF and SO2, or F2SO2 has been investigated at 4.2 K. The species formed when an HI/SO2 mixture is photolyzed has been identified as the symmetric σ radical HSO2. The assignment of the principal components of the g and hyperfine tensors was aided by our observation of preferential orientation of the trapped radical. The species formed when a CF3OF/SO2 mixture is photolyzed in the far uv has been identified as the symmetric σ radical FSO2. The g and A tensors have been determined from an exact solution of the spin Hamiltonian assuming a noncollinear tensor axis system.