Direct observation of spin-forbidden formation of O(1D) in the near-UV photolysis of ozone

Time-of-flight measurements have been made of the O(1D) fragment following the photolysis of ozone in the near-UV. At 321.9 nm fragments are seen with kinetic energies the values of which are those expected from spin-forbidden dissociation with ground state O2(X3Σg−) molecules as the co-product. Spin-allowed dissociation of internally excited ozone molecules is also seen to produce translationally cold O(1D) and O2(a1Δg) products. The implications for the dissociation of tropospheric ozone are briefly discussed.